They said they stalled the nomination because they wanted more information about their fellow Republican's post-Senate career, including certain foreign policy speeches and his private investment work.
"When the Senate returns on Feb. 26, there should have been sufficient time to consider Senator Hagel's record, so I will vote to end debate because I believe a president's Cabinet members deserve an up-or-down vote," Sen. Lamar Alexander, R-Tenn., said on the Senate floor Thursday.
Alexander said his own nomination to be education secretary during the George H.W. Bush administration was put on hold by Democrats, although not by filibuster.
Democrats delayed Alexander's nearly two months because they wanted more information about his alleged involvement in corrupt financial practices while he was Tennessee governor in the 1980s. Alexander was later unanimously confirmed.
The White House was concerned Thursday's delay would give Hagel opponents, including conservatives and pro-Israel forces, time to step up their efforts to crush his chances of being confirmed, The New York Times said.
White House spokesman Jay Carney accused Republicans of putting "political posturing ahead of our nation's security."
Delaying the vote while acknowledging Hagel will eventually win Senate confirmation "runs against both the majority will of the Senate and our nation's interest," Carney said.
"This waste of time is not without consequence," he said in a statement.
"We have 66,000 men and women deployed in Afghanistan, and we need our new secretary of defense to be a part of significant decisions about how we bring that war to a responsible end," Carney said.
"Next week in Brussels, the United States will meet with our allies to talk about the transition in Afghanistan at the NATO Defense Ministerial, and our next secretary of defense should be there," he said.
Instead, Leon Panetta will remain as defense secretary and travel to Brussels, the Pentagon said.
The failed 58-40 vote to block the filibuster represented the first time in history the Senate required a defense secretary nominee to clear a 60-vote hurdle before facing a final, simple majority vote.
Republicans insisted Democrats were trying to rush the nomination through.
"We didn't need to have this vote today," said Senate Minority Whip John Cornyn, R-Texas. "But the White House and the majority leader were determined to have this vote in order to try to get a story in the newspaper, one that misrepresents the nature of the objection on this side."
Majority Leader Harry Reid, D-Nev., accused senior Republicans of being "worried about primary elections" in 2014, in which Tea Party challengers might confront them for not sufficiently blocking Obama's Pentagon nominee.
"I guess to be able to run for the Senate as a Republican in most places of the country, you need to have a resume that says, 'I helped filibuster one of the president's nominees,'" Reid said.
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