This is a bluff by the Hagel naysayers. They don't have the votes and very soon, Harry Reid will hold another cloture vote. Right now, he is within one vote of prevailing.

New York Times:

But even as Republican senators tried to throw up another obstacle, Senate Democrats said they were pushing ahead with plans to hold a final up-or-down vote on the nomination no later than Wednesday.

Should that vote proceed as planned, Mr. Hagel's confirmation appears assured. Several Republicans have said that they intend to drop their attempts to filibuster the nomination.

But given how deeply divided Mr. Hagel's nomination has left the Senate, the outlook in the immediate term is murky.

Many Republicans, like the 15 who wrote to the president on Thursday, signaled that they would not let the issue die quietly. And those who have said that they would ultimately not support a filibuster, like Deb Fischer of Nebraska and Richard Shelby of Alabama, were leaving the door open to further delay.

Saying that Mr. Hagel's confirmation would be "unprecedented" because of near-unanimous opposition from Republicans, the group of 15 senators urged Mr. Obama to pick another candidate.

"Over the last half-century, no secretary of defense has been confirmed and taken office with more than three senators voting against him," they wrote. "The occupant of this critical office should be someone whose candidacy is neither controversial or divisive."

Forget the controversy and divisiveness. Hagel is unqualified, as he proved in his confirmation hearing. But if the president didn't withdraw his name after that troubling performance, he's not going to do it now.