The committee vote for Chuck Hagel to be defense secretary is set for tomorrow.

Top Republicans on the committee are threatening a walk out, but John McCain (R-AZ) isn't one of them.

“I will not participate in any walkout of tomorrow’s Committee vote – an action that would be disrespectful to Chairman [Carl] Levin and at odds with the best traditions of the Senate Armed Services Committee," said McCain, who previously served as ranking member of the committee.

McCain and Hagel, who both served in Vietnam, were Senate allies until Hagel split with McCain over his criticism of the surge in Iraq, which McCain proposed.

McCain gave Hagel a hard time for that stance during his confirmation hearing, demanding a yes or no answer to whether he was right or wrong about the surge. Hagel refused, and instead said Iraq may have been the worst foreign policy decision since Vietnam.

But, despite that tension, in the days since that uneven testimony, McCain, who says he's leaning against Hagel's nomination, has come to Hagel's defense, arguing against the outright blockage of Hagel's nomination.

Days after Majority Leader Mitch McConnell (R-KY) left open the possibility of filibustering Hagel's nomination, McCain came out against that.

Then, after Sens. Lindsey Graham (R-SC) and James Inhofe (R-OK), the current ranking member of Armed Services, said they would try to block Hagel, McCain is saying those efforts go too far.

For Hagel's part, NBC's Michael Isikoff talked to Chuck Hagel’s brother Tom, who says Chuck Hagel will not withdraw. In fact, he’s going to “fight harder.” Tom Hagel says the only way he’d withdraw is if the White House wanted him to, and the White House is sticking by him.

Majority Leader Harry Reid (D-NV) said he would hold a full Senate vote on Hagel either Wednesday or Thursday, reports NBC's Mike Viqueira.

EDITOR'S NOTE: A previous version of this post reported that McCain was going to vote against Hagel, but McCain has not made a final decision. He is, instead "leaning against" Hagel.