Senate Minority Leader Mitch McConnell, R-Ky., has said Republicans may filibuster the Chuck Hagel nomination, but Sen. John McCain, R-Ariz., a fierce critic of Hagel in his committee hearing last week, announced Monday that he will not back a filibuster to stop the confirmation, MSNBC reports.

At last week’s confirmation hearing for President Barack Obama’s defense secretary nominee before the Senate Armed Services Committee, McCain and Hagel clashed over the 2007 troop surge in Iraq, which Hagel opposed and McCain points to as a turning point in the Iraq war.

“Sen. Hagel did not do a very good job before the Armed Services Committee,” McConnell told Kentucky reporters Saturday, according to the Washington Post.  “I think the opposition to him is intensifying. Whether that means he will end up having to achieve 60 votes or 51 is not clear yet.”

McConnell did not say how he planned to vote, however.

McCain’s stature in the Senate, however, is expected to heavily influence the Republican caucus. Without a filibuster threat, Hagel needs just a simple majority to win confirmation. To defeat a filibuster, he must garner 60 votes.

Sen. Carl Levin, D-Mich., chairman of the Armed Services Committee, says all 53 Senate Democrats and two allied independents are poised to vote for confirmation, MSNBC reported. Any wavering Democrats largely fell in line following a meeting between Hagel and influential New York Sen. Chuck Schumer, which Schumer said allayed his concerns about past statements the defense nominee had made about Israel.

Republican Sens. Thad Cochran of Mississippi and Mike Johanns of Hagel’s Nebraska have indicated they will vote for Hagel’s confirmation, bringing the tally to 57. In a statement following Hagel’s testimony, Levin indicated that both Cochran and Sen. Lisa Murkowski, R-Alaska, would support Hagel.

But Murkowski still seemed undecided in an interview given to MSNBC Monday.

Along with Murkowski, Sens. Susan Collins of Maine and Bob Corker of Tennessee are seen as possible Hagel supporters among his fellow Republicans.

Sen. Roy Blunt, R-Mo., has said he will vote against Hagel but, like McCain, opposes a filibuster.

A filibuster of a Cabinet nominee would be unprecedented, and few have been voted down. The Senate Armed Services Committee and full chamber could vote on Hagel’s confirmation this week.