President Obama nominated Ms. Halligan for one of three vacancies on the U.S. Court of Appeals for the D.C. Circuit.
Mr. Obama expressed accused Republicans of undermining the judicial confirmation process for partisan purposes.
The Senate minority leader, Mitch McConnell, led the Republican Party’s opposition to the nomination, saying Ms. Halligan’s record demonstrated that she viewed the court as a means of advancing a social agenda instead of as a forum for deciding legal questions. During her confirmation hearing, Ms. Halligan distanced herself from positions she had taken for clients. Republicans, however, questioned whether she had been candid and portrayed her as an extremist.
Senate Democrats criticized the filibuster against Ms. Halligan. Senator Patrick J. Leahy, a Vermont Democrat who is the chairman of the Judiciary Committee, described her as a mainstream and well-qualified legal thinker who was being attacked by “concocted controversies and a blatant misreading” of her record.
Senator Charles E. Schumer of New York warned that the Republican action could undo a bipartisan agreement that has guided the way the Senate has handled appeals court nominations since 2005. The agreement, created by seven Democrats and seven Republicans known as the Gang of 14, was reached after Democrats employed the tactic to prevent up-or-down votes on several of President George W. Bush’s nominees.
Republicans at the time argued that it was unconstitutional to filibuster judicial nominees. The Republican leader, Senator Bill Frist, threatened to ban filibusters.
The crisis was averted after seven Democrats agreed not to block certain appeals court nominees. In exchange, seven Republicans promised not to change Senate rules.
Of the seven Republican senators who were part of the Gang of 14, four — John McCain of Arizona, Lindsey Graham of South Carolina, and Olympia J. Snowe and Susan Collins of Maine — are still serving. All voted against allowing a vote on Ms. Halligan.