Levin called Hagel "well-qualified." Feinstein described him as "a knowledgeable and independent voice with a strong grasp of the pressing national security issues facing our country." Reid said "few nominees have such a combination of strategic and personal knowledge of our national defense needs."
Sen. Patrick Leahy, D-Vt., said Hagel "is a combat veteran who still carries shrapnel in his body from his wounds. He will not need on-the-job training."
Several Democrats, most notably Sen. Chuck Schumer of New York, and a number of Republicans, including Jim Inhofe of Oklahoma and John McCain of Arizona, said they would await the Senate process and the opportunity to question Hagel. That raises the stakes for his private meetings with senators and his confirmation hearing in the next few weeks before the Armed Services Committee.
While some opposition was expected for Obama's nominee, no senator has threatened to block the selection. Republican and Democratic congressional aides said the White House wouldn't have put forth the nomination if it didn't think it had the votes for Hagel's confirmation. Democrats hold a 55-45 advantage in the Senate.
Former Sen. Max Cleland, D-Ga., himself a wounded Vietnam veteran, said he thinks Hagel "has to clarify" his positions on issues like Iran and Israel.
But Cleland also said in an interview on "CBS This Morning" Tuesday that Hagel is battle-tested and ready for the challenges of a confirmation process, accusing the Nebraskan's critics of "swatting at nothing, shadow-boxing."
Hagel's hopes rest on the willingness of senators to give a president his picks for the Cabinet, and the high threshold of deeming a nominee unfit for a civilian appointment. Politically, it would be remarkable for the Democratic-controlled Senate to deny Obama his nominee and undercut the president at the start of his second term and in the midst of fierce budget negotiations with Republicans.
The Senate has rejected one of its own in recent years.
In 1989, the Democratic-led Senate voted down the nomination of John Tower to serve as defense secretary over questions about the former Republican senator's personal life. It was an embarrassment to President George H.W. Bush, who then turned to Dick Cheney to lead the Pentagon.
While the Armed Services Committee decides Hagel's fate, the Senate Intelligence panel will decide on Brennan, 57, a close Obama adviser for the past four years.
Brennan withdrew from consideration for the spy agency's top job in 2008 amid questions about his connection to harsh interrogation techniques used during the George W. Bush administration. He is certain to face questions about the issue again from Democrats while Republicans press him on leaks of classified information in the Obama administration.
In announcing the nominations in the East Room, Obama urged the Senate to move quickly.
"When it comes to national security, we don't like to leave a lot of gaps between the time that one set of leaders transitions out and another transitions in," the president said.