"If it ended up on the front page of Drudge, I didn't say it right," she said, laughing.
Obama agreed and said she rejoices when she goes through the press clippings and finds no stories about her.
Asked if they agreed with former President Clinton, who told voters in 1992 that they would be getting "two for the price of one," Edwards said she disagreed.
"I think they're voting for the candidates," she said. "I try to be a good surrogate to try to convince people to go listen to him speak."
McCain, whose husband ran for the Republican nomination in 2000, said she thinks it's a fine line.
"I think the American people truly are electing both people, but from the spouse point of view, not in a leadership or decision making aspect."
McCain said the campaign has brought her and her husband closer because they are each other's greatest supporters and greatest critics. But campaigning for president becomes easier the second time, she said.
"Since 2000, I think I'm more comfortable in my skin, politically and other ways, I've learned to say no," McCain said.
Michelle Obama, a newbie when it comes to presidential campaigns, admitted she worried early on what her husband's bid would mean for her family.
"You always worry about your life getting sucked out from under you," said Obama.
"I'm very practical. I have to know how is this gonna play out. Barack is like 'Let's do it!,'" she said. "And I'm like, 'What about school?'"
"For me it was always thinking about the practical elements. How are we gonna make sure our kids are solid?" she said.
Obama, who has scaled back her public affairs position at a Chicago hospital to campaign for her husband, said she finds it therapeutic to talk to women on the campaign trail about struggling to balance work and family.
"We are the public representation of the challenges that we are all facing. That's what all of us as women are trying to figure out," she said. "We're juggling and we're challenged and we're overworked and we're overscheduled and we're not getting the support that we need."
Obama said when the going gets tough she leans on her mother, who gives her advice.
"I hear, 'Don't sweat the small stuff,'" Obama said. "And, 'He's a good man, don't be mad at him!' My mom is a huge support for me."
Romney, wife of millionaire Republican candidate Mitt Romney, said she doesn't "have input in strategy or anything like that" but said she often lobbies to have events taken off her husband's schedule.
"I weigh in all the time," she said. "'Don't work him so hard! Look at the schedule, you're killing the man!'" But Romney said they never fix it.
Romney said politics can take an enormous toll.
"We are so busy keeping it together for everybody that we forget about ourselves," Romney said. "I've been diagnosed with MS, Elizabeth is battling breast cancer. You find finally your body has given up."
Romney said that while she loved meeting voters in early voting states like Iowa and New Hampshire, she admitted she didn't like attending fundraisers.
"It's really very frustrating to have that be so much a part of the process," she said.
Romney said she was surprised to find how often she is asked to speak for her husband, but argued political spouses need more freedom to speak their minds.