It’s rare for the Senate to reject Cabinet nominees, particularly former senators, in part because lawmakers believe a president is entitled to his team and feel bigger fights are ahead.

Controversial nominees often withdraw before they get a vote, though not always. In 2009, Attorney General Eric Holder weathered a stormy confirmation hearing – and Republican-imposed delays – and was confirmed with 75 votes. Hagel almost certainly will need 60 votes to overcome procedural hurdles and win confirmation. Democrats control 55 seats.

Senate Majority Leader Harry Reid, D-Nev., issued a statement supporting the choice while Minority Leader Mitch McConnell, R-Ky. said Sunday on ABC’s “This Week” that Hagel would be given a fair hearing, but he would not say if he supported him. “I think he ought to be given a fair hearing, like any other nominee. And he will be,” McConnell said.

Hagel, who served in the Senate for two terms ending in 2009, alienated fellow Republicans by criticizing the management of the Iraq war after he initially supported the U.S.-led invasion, and more recently by endorsing former Democratic Sen. Bob Kerrey in the 2012 Nebraska Senate race against eventual winner Republican Deb Fischer.

Some backers of Israel have questioned his support for the country following statements he made about a “Jewish lobby” intimidating lawmakers and a mixed record over the imposition of sanctions on Iran. His defenders say he voted for nearly $40 billion in military aid to Israel over his tenure.

Log Cabin Republicans cited a 14-year-old quote to accuse Hagel of being anti-gay after he opposed the nomination of the ambassador to Luxembourg, arguing that an “openly, aggressively gay” man should not be selected to represent the U.S. He recently apologized to former Ambassador James Hormel, but the group continued to call his record on gay rights “dismal.”

“Until his name surfaced as a potential nominee for secretary of defense, he has stood firmly and aggressively against not only gay marriage, but also against gay people in general,” said Gregory T. Angelo, interim executive director of the Log Cabin Republicans, a national gay and lesbian Republican organization.

If confirmed, Hagel would take over the Pentagon at a critical time. Amid shrinking budgets, the new defense secretary will have to wrap up the war in Afghanistan, decide what do about Iran’s potential nuclear threat and how best to pursue the next step in the war on terror.

In brief remarks Monday, Hagel said he would always give Obama “my honest and most informed counsel.”

James Rosen and Jonathan S. Landay contributed to this report.