What's the difference between the presidential campaign before and after the national political conventions? Lipstick.

The colorful cosmetic has become a political buzzword, thanks to Republican vice presidential nominee Sarah Palin's joke in her acceptance speech that lipstick is the only thing that separates a hockey mom like her from a pit bull.

Democratic presidential nominee Barack Obama told an audience in Lebanon, Va., on Tuesday that GOP presidential nominee John McCain says he'll change Washington, but he's just like President Bush.

"You can put lipstick on a pig," he said to an outbreak of laughter, raucous applause and an ovation from his audience, clearly drawing a connection to Palin's joke. "It's still a pig. You can wrap an old fish in a piece of paper called change. It's still going to stink after eight years."

McCain's campaign immediately organized a telephone conference call in response and called on Obama to apologize for calling Palin a pig. Obama's campaign said he wasn't referring to Palin; he had been talking about McCain immediately before the lipstick comment.

Obama followed up by saying Palin is an interesting story, drawing boos at the mention of her name that he tried to cut off.

"Look, she's new, she hasn't been on the scene, she's got five kids. And my hat goes off to anybody whose looking after five. I've got two and they tire Michelle and me out," he said.

A questioner rose and asked Obama to join Republicans and agree that candidates' families and religion are off limits. Palin's pregnant teenage daughter and the teachings of her church, the nondenominational Wasilla Bible Church, have been the subject of scrutiny since McCain picked her as his running mate.

Obama responded that he already has said families are off limits and he's very protective of his daughters, 10-year-old Malia and 7-year-old Sasha. He said he doesn't want their inevitable future mistakes to become newspaper fodder if he gets to the White House.

Obama also is no stranger to attacks on his religion. He's been the subject of a false rumor campaign saying he's a Muslim, and the racially tinged sermons of his longtime former preacher caused problems for his campaign earlier this year.

He stressed that he's a Christian and "so the fact that Gov. Palin is deeply religious, that's a good thing." He said poking around in her religion or saying it's wrong is "offensive" and he wants to have a debate about the issues.

"But don't give people some sort of religious litmus test because I don't want somebody to question my faith and I'm certainly not going to question somebody else's," he said.