The Federal Election Commission has dismissed a complaint by an ally of President Donald J. Trump accusing the Democratic Party and one of its former consultants of violating campaign finance laws by working with Ukraine to help Hillary Clinton’s 2016 campaign by damaging Mr. Trump’s.

An unusual bipartisan combination of members of the commission voted against pursuing a complaint filed in 2017 by Matthew G. Whitaker, a former federal prosecutor and staunch defender of Mr. Trump who was later appointed acting attorney general.

He filed the complaint after Mr. Trump and his White House began publicly calling for investigations of the matter in an effort to deflect attention from revelations that Mr. Trump’s son Donald Trump Jr. and other campaign advisers met with a Kremlin-connected Russian lawyer at Trump Tower during the 2016 campaign.

Mr. Whitaker claimed in his complaint that the Democratic National Committee and a consultant who had worked for it, Alexandra Chalupa, violated a prohibition on foreign donations by soliciting damaging information and statements from Ukrainian government officials about Paul Manafort, who was Mr. Trump’s campaign chairman at the time.

The commission — which is composed of three members selected by each party — voted 4 to 2 in April that there was not probable cause to believe that Ms. Chalupa and the Democratic National Committee broke the law, according to documents released Wednesday.

The four commissioners voted against a recommendation by the commission’s general counsel to find probable cause that Ms. Chalupa and the Democratic National Committee violated the foreign donation ban by trying to arrange an interview in which Petro O. Poroshenko, the Ukrainian president at the time, might say something critical about Mr. Manafort.

While the four commissioners issued statements disputing the general counsel’s characterization that Ms. Chalupa’s communications with the embassy prompted the ban, they also offered very different ideological concerns.

The three Republican commissioners said in a statement accompanying the decision that they had “grave constitutional and prudential concerns” about the general counsel’s reading of the law, which they cast as an overreach. Ms. Chalupa’s communication with the embassy, they wrote, “did not ask that Ukrainian officials convey a thing of value within the meaning of a ‘contribution’ to the D.N.C.”

The Republicans were joined in voting against probable cause by Ellen L. Weintraub, a Democratic commissioner since 2002, who cited concerns about Russian disinformation as a basis for her vote.

Bipartisan votes have become more rare in commission enforcement matters in recent years, as Democratic commissioners who tend to favor stricter campaign finance rules have sometimes found themselves at loggerheads with their Republican colleagues, who tend to oppose campaign finance restrictions as burdensome infringements on free speech.

The result has been deadlocked votes that effectively block the pursuit of cases.

The dismissal of the complaint by Mr. Whitaker came amid a flurry of deadlock votes as the commission works its way through a backlog of matters related to the 2016 presidential election.

Mr. Whitaker’s complaint, which was filed in his capacity as the executive director of a conservative watchdog group called the Foundation for Accountability and Civic Trust, asserted that the Trump Tower meeting presented “comparable circumstances” to the Ukrainian matter.

The complaint was based on an article in Politico revealing that Ms. Chalupa had discussions with officials in the Ukrainian embassy in Washington about Mr. Manafort’s work for Russia-aligned Ukrainian politicians.

Mr. Trump and his allies seized on the report, with the president suggesting on Twitter that his attorney general should investigate the matter, and his press secretary telling reporters, “If you’re looking for an example of a campaign coordinating with a foreign country or a foreign source, look no further than the D.N.C., who actually coordinated opposition research with the Ukrainian Embassy.”

Andrii Telizhenko, a former official at the embassy who was quoted in the article discussing Ms. Chalupa, was penalized in January by the Treasury Department for being part of what it called “a Russia-linked foreign influence network” that spread “fraudulent and unsubstantiated allegations” about President Biden during the 2020 campaign.

While the Treasury Department did not accuse Mr. Telizhenko of spreading disinformation during the 2016 campaign, Ms. Weintraub said in a statement that the assertions by the Treasury Department and others “completely undermined the credibility of the complaint” based on his claims.

Mr. Telizhenko, who provided testimony to commission staff, said in an interview that he stood by his claims, and rejected claims of connections to the Russian influence network cited by the Treasury Department.

Nonetheless, the F.E.C.’s handling of the matter is something of a repudiation to Mr. Trump, particularly given that Republican commissioners he nominated voted that there was not probable cause to believe a violation had been committed.

Ms. Chalupa, the Democratic National Committee and the Foundation for Accountability and Civic Trust did not respond to requests for comment.