A poll by Reuters shows that 29 senators were either committed to approving the nomination or leaning that way, while 17 were outright opposed or inclined that way.
Senate leaders need to secure a super-majority of 60 votes in the 100-member chamber to overcome efforts by some senators to block the nomination.
The needed votes seemed assured until last week when a handful of lawmakers, including two Senate Democrats on Friday, said they would not support Bernanke because of anger over his handling of Wall Street bailouts. The uncertainty sent stock markets down sharply on Friday, although they recovered some losses on Monday as Bernanke's approval looked more certain.
President Obama contacted the Democratic Senate leadership on Saturday and the White House dispatched advisers to the Sunday talk shows to muster support.
Bernanke's first four-year term as chairman expires on Sunday. If he is not confirmed in time, the Fed's vice chairman, Donald Kohn, is poised to take over on an acting basis. A vote could come as early as Wednesday.