Chuck Hagel is expected to be sworn in as U.S. defense secretary Wednesday, battered politically by a confirmation fight even as he faces challenges from Pentagon budget cuts to withdrawing U.S. forces from Afghanistan.

Hagel, 66, won Senate approval on a 58-41 vote Tuesday after months of Republican opposition that began even before President Barack Obama nominated him for the job. While Obama said that Hagel won "bipartisan confirmation," only four Republicans joined 52 Democrats and two independents to back him.

"He will take office with the weakest support of any defense secretary in modern history, which will make him less effective in his job," Sen. John Cornyn of Texas said during debate Tuesday.