delivered the opinion of the Court.

The Federal Election Campaign Act of 1971, 86 Stat. 11, as amended, 2 U. S. C. §431 et seq. (1976 ed. and Supp. IV), limits the contributions that may be made to candidates or political committees in an election for federal office. One provision of the Act, § 441a(d), authorizes limited expenditures by the national and state committees of a political party in connection with a general election campaign for federal office. After authorizing such expenditures, which otherwise would be impermissible,^[1] the section specifies the amount a[*29] national committee may spend in connection with a Presidential campaign, §441a(d)(2), and limits the amount that national and state committees of a political party may spend in connection with the general election campaign of a candidate for the Senate or the House of Representatives, § 441a(d)(3). In this litigation we examine whether § 441a(d)(3) is violated when a state committee of a political party designates the national senatorial campaign committee of that party as its agent for the purpose of making expenditures allowed by the Act.

I

The National Republican Senatorial Committee (NRSC) is a political committee organized specifically to support Republican candidates in elections for the United States Senate. Although the NRSC is authorized by § 441a(h) to contribute up to $17,500 to a candidate for election to the Senate, it is not given authority by § 441a(d) to make expenditures on behalf of such candidates, and it is the position of the Federal Election Commission, the agency charged with enforcement of the Act, that the NRSC may not do so on its own account. The Commission, however, has permitted the NRSC to act as the agent of national and state party committees in making expenditures on their behalf.

[*30] In February 1977, in response to an inquiry submitted late in 1976, the Commission issued an Advisory Opinion, 1976-108, that it would be consistent with the Act for the NRSC to spend its own funds in support of congressional candidates as the designated agent of the Republican National Committee (RNC). In April 1977, the Commission issued a regulation, 11 CFR § 110.7(a)(4) (1981), which provides that the national party committees may make expenditures in the general election campaign for President “through any designated agent, including state and subordinate party committees.” On the basis of this regulatory authority, the National Committee of the Democratic Party entered into an agreement specifying the Democratic Senatorial Campaign Committee (DSCC) as its agent for the expenditure of authorized funds in Senate campaigns. In 1978, certain state Republican Party committees designated the NRSC as their agent for §441a(d)(3) expenditure purposes.^[2] Complaints were filed with the Commission challenging this practice as inconsistent with the Act. In dismissing these complaints, the Commission twice ruled by unanimous votes that the agency arrangements were not forbidden by the Act. In re National Republican Senatorial Committee, Federal Election Commission Matter Under Review (MUR) 780 (Jan. 19, 1979); In re National Republican Senatorial Committee, Federal Election Commission MUR 820 (June 17, 1979). In 1980, certain state committees again designated the NRSC as their agent, and on May 19, the DSCC filed its complaint with the Commission asserting that the NRSC’s agreements with the state committees were contrary to § 441a(d)(3). The complaint did not challenge the contemporaneous agency agreement under which the NRSC acted as the agent of the RNC in connection with the latter’s expenditures under § 441a(d).[*31] After considering the report of its General Counsel, the Commission unanimously dismissed the complaint, concluding that there was “no reason to believe” that the agreements violated the Act.

The DSCC petitioned for review in the District Court for the District of Columbia pursuant to §437g(a)(8).^[3] That court granted the Commission’s motion for summary judgment, concluding that the decision of the Commission was not “arbitrary, capricious, an abuse of discretion or otherwise not in accordance with law.” Democratic Senatorial Campaign Committee v. Federal Election Comm’n, No. 80-1903 (DC Aug. 28, 1980) (reprinted at App. to Pet. for Cert, of NRSC B4). On appeal, the Court of Appeals for the District of Columbia Circuit granted the NRSC leave to intervene and reversed the judgment of the District Court after concluding that the “plain language of Section 441a(d)(3) precludes” the agency agreements between state committees and the NRSC. 212 U. S. App. D. C. 374, 383, 660 F. 2d 773, 782. We granted the petitions for certiorari filed by the Commission and the NRSC, 450 U. S. 964 (1981), and we now reverse the judgment of the Court of Appeals.

I — I I — 1

Although the Court of Appeals first addressed whether and to what extent it should defer to the Commission’s construction of the Act, 212 U. S. App. D. C., at 377, 660 F. 2d, at 776, this discussion and the conclusion that little or no deference was due the Commission were pointless if the court was correct that the agency agreements violated the plain language of the Act as well as the statutory purposes revealed by the legislative history. The interpretation put[*32] on the statute by the agency charged with administering it is entitled to deference, NLRB v. Bell Aerospace Co., 416 U. S. 267, 275 (1974); Udall v. Tallman, 380 U. S. 1, 16 (1965), but the courts are the final authorities on issues of statutory construction. They must reject administrative constructions of the statute, whether reached by adjudication or by rulemaking, that are inconsistent with the statutory mandate or that frustrate the policy that Congress sought to implement. SEC v. Sloan, 436 U. S. 103, 118 (1978); FMC v. SeatrainLines, Inc., 411 U. S. 726, 745-746 (1973); Volkswagenwerk v. FMC, 390 U. S. 261, 272 (1968); NLRB v. Brown, 380 U. S. 278, 291 (1965). Accordingly, the crucial issue at the outset is whether the Court of Appeals correctly construed the Act. For the reasons that follow, we disagree with the Court of Appeals. As we understand the Act and its legislative history, § 441a(d)(3) does not foreclose the use of agency agreements. The Commission thus acted within the authority vested in it by Congress when it determined to permit such agreements.

Section 441a(d)(3) provides as follows:

“The national committee of a political party, or a State committee of a political party, including any subordinate committee of a State committee, may not make any expenditures in connection with the general election campaign of a candidate for Federal office in a State who is affiliated with such party which exceeds—

“(A) in the case of a candidate for election to the office of Senator, or of Representative from a State which is entitled to only one Representative, the greater of—

“(i) 2 cents multiplied by the voting age population of the State (as certified under subsection (e) of this section); or

“(ii) $20,000; and

“(B) in the case of a candidate for election to the office of Representative, Delegate, or Resident Commissioner in any other State, $10,000.”

[*33] It is evident from its terms that the section does not in so many words forbid the state or national party to designate agents for expenditure purposes. This much is common ground. The Court of Appeals, however, held that because § 441a(d)(3) permits expenditures in congressional campaigns to be made by national and state committees of the political parties, including subordinate committees of the latter, and because the NRSC was neither a national committee^[4] nor a state committee, it should not be permitted to make expenditures under any arrangement “by which the special authority of a named entity is transferred to another.” 212 U. S. App. D. C., at 380, 660 F. 2d, at 779. Obviously, §441a(d) (3) does not permit the NRSC to make expenditures in its own right. But, contrary to the Court of Appeals, it does not follow that the NRSC may not act as an agent of a committee that is expressly authorized to make expenditures. In the nature of things, a committee must act through its employees and agents, as the Court of Appeals recognized, and nothing in the statute suggests that a state committee may not designate another committee to be its alter ego and to act in its behalf for the purposes of §441a(d)(3). To foreclose such an arrangement on the grounds that the named agent is not one of the authorized spenders under § 441a(d)(3) would foreclose all agency agreements regardless of the identity of the agent and regardless of the terms of the agency.^[5] Nothing in the Act demands that the choices available to the state committee should be so severely restricted.

[*34] If the Court of Appeals is correct that any arrangement is forbidden by which an authorized committee empowers another to exercise its spending authority, then neither of the national committees could legally enter into agency relationships with its congressional campaign committees. Yet, both have regularly done so, and respondent DSCC does not challenge these arrangements. Indeed, the DSCC accepts the Commission’s regulation, 11 CFR § 110.7 (1981),^[6] as valid and interprets that regulation as authorizing the agency agreements which have existed between the parties’ national committees and the Republican and Democratic Senatorial Campaign Committees.^[7] Moreover, when the Commission, as required by law,^[8] submitted the regulation to Congress, neither House expressed disapproval.

Despite this indication that Congress does not look unfavorably upon the NRSC’s sharing in the spending authority[*35] of § 441a(d)(3), the Court of Appeals reads such disapproval into Congress’ failure to explicitly provide for such arrangements. To bolster its argument, the court points to §441a(h),^[9] which directly authorizes the national party committees, including the Republican or Democratic Senatorial Campaign Committees, to contribute up to $17,500 to a senatorial candidate. This argument, if accepted, would only underline that the NRSC may not make additional expenditures on its own account. It does not answer the question whether a state committee may exercise its statutory spending authority by designating the NRSC as its agent for this purpose.^[10]

Neither does the legislative history of the Act purport to disapprove agency arrangements. The Court of Appeals refers to the defeat of the Brock Amendment, which would have exempted congressional campaign committees such as the NRSC from the Act’s expenditure limits.^[11] 212 U. S. App. D. C., at 381, 660 F. 2d, at 780. But rejection of a proposal to permit congressional campaign committees to make expenditures in their own right does not necessarily affect their capacity to perform agency functions. Moreover, insofar as the intent of Congress is reflected in its failure to adopt a proposed amendment, a contrary — and indeed stronger — inference can be found in the rejection by the 96th Congress of an amendment that would have expressly[*36] prohibited the movement of funds between state and national committees of a political party.^[12]

It is clear enough to us without saying more that the statute does not expressly or by necessary implication foreclose the agency agreements at issue in this case. But neither does it expressly permit or require such agreements. If this were a direct enforcement action rather than the review of a decision by the administrative agency charged with the enforcement of the statute, it may be that a court could defensibly arrive at the conclusion that agency agreements of this kind should be forbidden. It may also be that the Commission could have construed the statute to forbid the agreements and that a court would have accepted such a construction by the agency. But that is not this case. The Commission, in dismissing the DSCC’s complaint, has determined that agency agreements are not contrary to law and the question is whether the courts should defer to this judgment as a permissible construction of the Act or instead disregard the agency’s view and proceed to construe the statute based on its own view of what would best serve the purpose and policy of the Act.

Ill

The Court of Appeals determined that the Commission’s construction of the Act was entitled to no deference whatso[*37]ever. While acknowledging that deference is often appropriately given to an agency’s interpretation of its governing statute, the court refused to accord that deference here because of what it perceived as the lack of a reasoned and consistent explanation by the Commission in support of its decision. We agree that the thoroughness, validity, and consistency of an agency’s reasoning are factors that bear upon the amount of deference to be given an agency’s ruling. See Adamo Wrecking Co. v. United States, 434 U. S. 275, 287, n. 5 (1978); Skidmore v. Swift & Co., 323 U. S. 134, 140 (1944). We do not agree, however, that the Commission failed to merit that deference in this case.

Initially, we note that the Commission is precisely the type of agency to which deference should presumptively be afforded. Congress has vested the Commission with “primary and substantial responsibility for administering and enforcing the Act,” Buckley v. Valeo, 424 U. S. 1, 109 (1976), providing the agency with “extensive rulemaking and adjudicative powers.” Id., at 110. It is authorized to “formulate general policy with respect to the administration of this Act,” §437d(a)(9), and has the “sole discretionary power” to determine in the first instance whether or not a civil violation of the Act has occurred. 424 U. S., at 112, n. 153. Moreover, the Commission is inherently bipartisan in that no more than three of its six voting members may be of the same political party, §437c(a)(l), and it must decide issues charged with the dynamics of party politics, often under the pressure of an impending election. For these reasons, Congress wisely provided that the Commission’s dismissal of a complaint should be reversed only if “contrary to law.” §437g(a)(8).

The Commission’s position on the question before us is clear. Since 1976, it consistently has adhered to its construction of § 441a(d)(3) as not forbidding intraparty agency agreements. The Commission has on three separate occasions, all by unanimous votes, rejected the DSCC’s claim.[*38] On each occasion the Commission followed the recommendation of its General Counsel. In his first report,^[13] the General Counsel emphasized the absence of any specific statutory prohibition of the agency arrangements, and also relied on §441a(a)(4),^[14] which permits unlimited transfer of funds among state and national political committees of the same party. The second report,^[15] without rejecting any of the earlier arguments, also drew support from a Commission regulation approving similar agency agreements between national level committees.^[16] The third report,^[17] issued in this case, added an analysis of § 441a(d)(3), reviewed the legislative history, and took note of the fact that Congress had recently amended the Act with knowledge of the Commission’s construction of § 441a(d)(3) and had let that construction stand. Unlike the Court of Appeals, we find the differences in emphasis in the three reports of little significance. All reach the same conclusion, none rejects the arguments of the others.^[18] The Commission consistently has upheld the agency agreements; the fact that Commission Counsel has had the luxury of a number of sound arguments on which to base his opinions does not detract from the deference due the agency’s interpretations.^[19]

[*39] Hence, in determining whether the Commission’s action was “contrary to law,” the task for the Court of Appeals was not to interpret the statute as it thought best but rather the narrower inquiry into whether the Commission’s construction was “sufficiently reasonable” to be accepted by a reviewing court. Train v. Natural Resources Defense Council, 421 U. S. 60, 75 (1975); Zenith Radio Corp. v. United States, 437 U. S. 443, 450 (1978). To satisfy this standard it is not necessary for a court to find that the agency’s construction was the only reasonable one or even the reading the court would have reached if the question initially had arisen in a judicial proceeding.- Ibid.; Udall v. Tallman, 380 U. S., at 16; Unemployment Compensation Comm’n v. Aragon, 329 U. S. 143, 153 (1946). Under this standard, we think the District Court was correct in accepting the Commission’s judgment.

As we have said, § 441a(d) does not expressly or by implication forbid agency agreements. Although the Court of Appeals and the DSCC are of the view that since the section specifically authorized only two committees — the national and state party committees — to make campaign expenditures, no other committee could make such expenditures either on its own account or on behalf of others. But the opposite reading makes equal sense: Congress, having written the statute so precisely, would have made clear that expendi[*40]tures by other committees, whether by agency or otherwise, were prohibited.

We also find acceptable the Commission’s view that the agency agreements were logically consistent with §441a (a)(4). That section authorizes the transfer of funds among national, state, and local committees of the same party. There can be little question but that the section applies to the National Republican Senatorial Committee, as that Committee is part of the Republican Party organization.^[20] Under that provision, by using direct money transfers, instead of an agency agreement, the national committee could write a check to the state committee for the same amount that it would otherwise have spent directly under the agency agreement. That being so, we agree with the dissent below that the difference is “purely one of form, not substance.” 212 U. S. App. D. C., at 386, 660 F. 2d, at 785.

Money transferred to the state committee presumably would be spent as the state committee decided. Agency[*41] agreements, by comparison, might allow the NRSC to determine what expenditures to make on behalf of the state committees. The Court of Appeals made much of this, asserting that the agency arrangements, unlike §441a(a)(4) transfers, reduced the state committees to “legal shells.” The court overlooks that the NRSC easily could insist that funds transferred to a state committee be utilized in a certain manner. Conversely, state committees could retain or share control over how § 441a(d)(3) spending authority is exercised by writing conditions into the agency agreement. More fundamentally, state committees are not obligated to enter into agency agreements in the first place. The delegation of spending authority is an option, not a requirement, and it is an option resting entirely with the state committees.

Finally, the Commission’s interpretation is not inconsistent with any discernible purpose of the Act. In Buckley v. Valeo, we recognized that the primary interest served by the Act is the prevention of corruption and the appearance of corruption spawned by the real or imagined coercive influence of large financial contributions on candidates’ positions and on their actions if elected to office. 424 U. S., at 25. It has not been suggested that this basic purpose of the Act is compromised by agency arrangements. Since the limitations on the amount that can be spent under the Act apply with equal force whether a state committee exercises its authority directly or transfers it to one of the party’s national committees, an agency arrangement does not permit the expenditure of a single additional dollar.

Section 441a(d)(3) fits into the general scheme by assuring that political parties will continue to have an important role in federal elections.^[21] Although the DSCC would transform this purpose into the more specific objective of stimulating political parties at the state level, none of the limited legisla[*42]tive history concerning the provision supports this view.^[22] The legislative discussion of preserving a role for political parties did not differentiate between the state and national branches of the party unit. It is hardly unreasonable to suppose that the political parties were fully capable of structuring their expenditures so as to achieve the greatest possible return. Agency agreements may permit all party committees to benefit from fundraising, media expertise, and economies of scale. In turn, effective use of party resources in support of party candidates may encourage candidate loyalty and responsiveness to the party. Indeed, the very posture of these cases betrays the weakness of respondent’s argument — an argument that, at bottom, features one of the two great American political parties insisting that its rival requires judicial assistance in discovering how a legislative enactment operates to its benefit.

Thus, the absence of a prohibition on the agency arrangements at issue, the lack of a clearly enunciated legislative purpose to that effect, and indeed, the countervailing existence of a transfer mechanism whose presence is difficult to reconcile with the interpretation urged by the Court of Appeals, prevent us from finding that the Commission’s deter[*43]mination was “contrary to law.” Therefore, the judgment of the Court of Appeals is

Reversed.