Mr Reid added that the president remained a formidable campaigner and fund-raiser and should not be ruled out of the fight in 2012. But he said some Democrats were feeling "buyer's remorse" for selecting the president in his epic battle with Mrs Clinton for the 2008 Democratic nomination.

"The notion everyone is talking about is 'is he Jimmy Carter or will he be a one-term president'," he said.

Gary Pearce, a Democratic strategist in North Carolina, a swing state Mr Obama is likely to struggle to retain in 2012, said: "Democrats are worried. He looks weak, he doesn't say anything that grabs you, and people are looking for some kind of magic."

He said some activists were asking "do we need someone tougher to fight the tea party?" "You see a yearning for a Bill Clinton-type approach and Hillary would reflect that. Obama is just a different political animal, he is a low-key guy," he added.