Levin faces a conundrum: He has the ability to force a Hagel vote through the committee on a party-line vote, since Democrats outnumber Republicans. But doing so could damage the committee’s longtime bipartisan spirit.

Last Thursday’s hearing with Panetta alarmed Levin, Democrats said. Levin worries the aggressive, pointed questioning that Republicans directed at Panetta over the Sept. 11 attacks in Benghazi, Libya, could signal some Republicans simply will not compromise on the issue of Hagel’s nomination.

“Fed up is the right term for [Levin’s mood],” said a Democratic source. “After the Benghazi hearing, it showed what we are dealing with on the Republican side.”