Senator Mitch McConnell of Kentucky, the Republican leader, called the president’s move “yet another episode of choosing a partisan path despite bipartisan opposition.”

Another Republican, Senator Tom Coburn of Oklahoma, said in an interview that he could understand Mr. Obama’s frustration; he said that most of the other nominees were noncontroversial and that his concern was centered primarily on Mr. Becker. “He has a precedent,” Mr. Coburn said of the president, “Others have done it, so I’m not critical of him doing it. But I am critical of the Becker appointment because he doesn’t have the votes.”

Recess appointments are a common tool for presidents frustrated by the confirmation process. Mr. Obama’s action puts him on a par with Mr. Bush, who had made 15 recess appointments by this point in his presidency. Mr. Bush had an especially intense tussle with Democrats over judicial appointees; during the course of his two terms in office, he made a total of 171 recess appointments, although 72 were to part-time positions, according to the Congressional Research Service. President Clinton made 139 recess appointments.

With the exception of Mr. Becker, the White House said most of the 15 nominees being installed by Mr. Obama have bipartisan support. Indeed, in a sign that Mr. Obama did not want to go too far in inflaming partisan passions, he resisted using his executive powers to install one of his most contentious candidates, Dawn Johnsen, an Indiana University law professor, to lead the Office of Legal Counsel at the Justice Department. Ms. Johnsen has drawn the ire of Republicans for her work as a lawyer for NARAL Pro-Choice America as well as her outspoken opposition to the Bush administration’s counterterrorism policies.

Saturday’s announcement is certain to cheer some of Mr. Obama’s strongest supporters, who have been arguing that the president should take on Republicans in a more forceful way. Gay rights advocates were elated to see Chai R. Feldblum, a Georgetown University Law professor who advocates on gay issues, claim a spot on the Equal Employment Opportunity Commission as a result of Mr. Obama’s action.

But perhaps no group will be as heartened as union leaders.

For months they had complained that Mr. Obama was too timid in responding to Republican opposition to Mr. Becker, a former associate general counsel for the A.F.L.-C.I.O. and the Service Employees International Union. Labor leaders were also unhappy that the labor relations board has been largely paralyzed since January 2008 because only two of its five seats have been filled since then. Mr. Obama also appointed Mark Pearce, a New York labor lawyer, on Saturday to fill a fourth seat on the board.

Last month, the Democrats fell eight votes short of the 60 needed to overcome a threatened Republican filibuster of a vote for Mr. Becker. Two Democrats, Blanche Lincoln of Arkansas and Ben Nelson of Nebraska, joined Republicans in the 52-to-33 vote.