Appearing on the light-hearted chat show Late Show with David Letterman, Clinton also spoke of her fatigue on the gruelling campaign trail a day before the "Super Tuesday" flood of nomination ballots in 24 states.

Letterman asked how she proposed to stop Bill Clinton rifling through her things in the Oval Office if she is elected President.

"In my White House we will know who wears the pant suits," the New York senator said.

"I have a very passionate defender in my husband. I'm proud he's enthusiastic about my campaign," she said after prominent Democrats criticised the former President's outspoken attacks on Democratic rival Barack Obama.

Bill Clinton has been more restrained on the campaign trail of late, but his wife denied that she had been forced to intervene to tone down his rhetoric.

"It was more like, you know, I think that we need to get back on the positive here. Because this campaign really needs to be about the future," she said.

The economy was top of the list of voters' concerns, Clinton said.

"When there's not something that's really dominating the news, then people kind of lean back and think OK, would I want to have a beer with this person?