Members of the Senate have left Washington for the President’s Day break, scheduled to return February 25. That means Republicans who voted to filibuster the nomination of Chuck Hagel to be Defense Secretary have ten days to search for new evidence against him and lobby colleagues to keep up the opposition.

With 41 votes needed to uphold a filibuster — exactly the number Republicans mustered against Hagel on Thursday — the GOP has no votes to lose. And the most critical of those votes appears to belong to Sen. John McCain.

“McCain is the one to watch on this,” says one senior Republican Senate aide. “He seems wiling to vote for cloture on the grounds that cloture should be invoked on cabinet-level nominees.”

What the aide meant is that McCain supported the Republican filibuster Thursday not because he believes Hagel should never receive an up-or-down vote but because McCain wanted to delay Hagel as a way to pressure the Obama administration to release more information on the deadly September 11, 2012 attack on the American consulate in Benghazi.

In fact, McCain has said clearly that he believes Hagel is entitled to a final vote, something that would surely result in Hagel’s confirmation, given overwhelming — so far unanimous — Democratic support. But at the same time, McCain joined the filibuster, at least for the moment, to squeeze more details about Benghazi out of the administration. “We deserve answers before we move forward with nominees,” McCain told reporters Wednesday. “That’s been the standard I’ve pursued for the past 26 years.”

Now, the task of Republicans trying to kill the Hagel nomination is to convince McCain to change his mind on whether Hagel deserves an up-or-down vote. The ten-day break gives those Republicans, including freshman Sen. Ted Cruz, who has taken a leading role in opposing Hagel and in seeking more time to investigate Hagel’s record, an opportunity to convince McCain to stay with the filibuster after the President’s Day break.

It could be a tough job. McCain is not only a Republican leader on all things military who was apparently irritated by Cruz’s remarks about Hagel at an Armed Services Committee meeting Tuesday. McCain is also a headstrong and sometimes difficult man who can react badly if he feels he is being pressured. So look for GOP senators to be as diplomatic as possible in the effort to convince McCain that Hagel should be stopped without ever receiving a confirmation vote.

Hagel opponents will also seek to convince McCain’s allies, Sens. Lindsey Graham and Kelly Ayotte, that they should continue to filibuster Hagel even if their demands on Benghazi have been (somewhat) satisfied. Indeed, in the absence of any Democratic defections, the anti-Hagel group needs to keep McCain, Graham, and Ayotte — plus every other Republican who voted against Hagel on Thursday — in the fold if they expect to use the filibuster to actually stop the Hagel nomination.