RACINE, WI - A young woman just asked Senator McCain if he'd gone back on his promise not to "sling mud" in this campaign with the ad his campaign released yesterday comparing Obama to Britney Spears and Paris Hilton. McCain responded that there are contrasts to be drawn and his campaign is merely drawing them based on substance, not style.

"Campaigns are tough, but I'm proud of the campaign we're running," McCain told the crowd. "We're proud of that commercial."

UPDATE: Here's the full quote, transcribed from tape:

First of all, let me say that there are differences, and we drawing those differences. I said earlier that I admire his campaign, but what we're talking about here is substance and not style. Campaigns are tough, but I'm proud of the campaign that we have run, I'm proud of the issues we are trying to address with the American people. And, again, I would hope that Senator Obama would join me so that we could discuss this - as he said he wanted a "duel" over taxes, as I think he said yesterday.

All I can say is that we are proud of that commercial. We think Americans need to know that I believe that we should be basing this campaign on what we can do for Americans here at home and how we can make America safe and prosperous, and that's the theme of my campaign.

I should also note that the crowd responded very favorably to McCain's answer.

Indeed, the very next questioner from the audience was another young woman who announced to the crowd: "I'm 18 and I just have to say that Obama, like, terrifies me. And I would just like to say I think you need to call him on every shot. Don't let him get away with a single thing. We can't afford it." This, too, generated hearty applause from the crowd.