Senate Majority Leader Harry M. Reid (D-Nev.) filed a motion Wednesday afternoon to begin the confirmation debate of Defense Secretary nominee Chuck Hagel, setting up a vote by at least Friday morning that would require 60 votes to cut off a potential filibuster by conservative Republicans.

Democrats had been hoping to avoid needing a super-majority to clear the confirmation hurdles for Hagel, a former GOP senator from Nebraska whose centrist views on national security drew stern rebukes from his former Senate Republican colleagues during hearings before the Armed Services Committee last week. Moreover, Hagel's nomination has become ensnared in the ongoing fight by senior GOP hawks, led by Sens. John McCain (R-Ariz.) and Lindsey Graham (R-S.C.), to extract more information about the response to the Sept. 11 attack on a U.S. diplomatic outpost in Benghazi -- their latest request coming in a letter this week asking President Obama to explain whether he ever requested the Libyan government for help during the eight hour siege.

Reid, in filing the anti-filibuster motion, lamented the unusual step of needing 60 votes to win confirmation of a cabinet-level nominee.

"What a shame, that's the way it is," Reid said.

McCain and Graham have tried to argue that they are not technically supporting a filibuster of Hagel, just holding up his confirmation until they get more information from the White House. A distinction without a difference, the impact is the same: If Hagel does not get 60 votes, his nomination lingers in limbo.

Already counting on 55 votes from Democrats, Reid will need five Republican votes, and early indications are that they are very close or already over that mark.

A pair of GOP veterans, Thad Cochran (Miss.) and Mike Johanns (Neb.), have already announced they will vote to confirm their former colleague. Several others indicated they would vote to end a filibuster, but then vote against confirming Hagel on final passage, as Sen. Susan Collins (Maine) said on Thursday.

The vote must be held by Friday, under Senate procedures, but the chamber could agree to hold a roll call by Thursday evening. If he clears the 60-vote mark, the chamber would likely then quickly move to a full confirmation vote.