John McCain says the more people get to know his running mate, the more they'll "love her."

He tells Fox News that he's "confident" she'll do fine in tonight's debate against Joe Biden. He says, "She's smart, she's tough" and has been in debates before.

McCain also dismissed suggestions he was upset with his staff for holding Palin back and not letting her be herself on the campaign trail. As he put it, "We let Sarah be Sarah."

Tonight's 90-minute event in St. Louis will be Palin's first lengthy give-and-take session since joining the GOP ticket. It's hosted by PBS anchor Gwen Ifill, who is writing a book on blacks and politics, with a chapter on Barack Obama.

McCain said he wished "they had picked a moderator that isn't writing a book favorable" to his opponent. But he says he's sure Ifill will act as the "professional journalist that she is."