The Republican YouTube debate hasn't even begun, and it's already obsolete. Why? Because all of the questions that we'll hear tonight were submitted by YouTube users before the Politico broke today's blockbuster news that Rudy Giuliani expensed his adulterous trysts in the Hamptons to NYC taxpayers, then tried to cover it up. And consequently, CNN is left with a curious irony -- the debate stage in St. Petersburg is going to be the only place in America where folks talking about politics won't be discussing the biggest news in politics. Because after today, the Republican race won't look the same.

Beginning tonight, Rudy is more likely than not done as a serious candidate.

Barring a remarkable explanation from the Giuliani campaign or a superlatively craven trad med press meltdown, Rudy's campaign is likely to be destroyed by this story. Two things capture the American attention like no other: sex and money. Only scandals involving sex or money garner any serious public interest. Even then, a money scandal without sex leads most Americans to yawn. And dogged persistence can outlast most sex scandals (see Vitter, David). But when you combine the two -- when you add adultery to misappropriation of taxpayer money -- magical things happen. It's like that beautiful chemical reaction when heat, yeast, and sugar meet. There's an unusual smell, then lots of hot air, and then everything blows up real big. People can't turn their eyes away from the unholy marriage of lust and lucre. And no amount of 9/11ing can distract the attention of a wild-eyed press from the shame.

We're already seeing the beginning of the end. Rudy's friends are deserting him faster than he deserted Bernie Kerik (interestingly enough, another guy who expensed his adultery to hardworking New Yorkers). The story is topping Drudge. Fox News -- the network accused by rival GOP campaigns of being in the bag for Rudy -- has independently "confirmed" the news, and made it their top story on their web page. Christ, when Drudge and Roger Ailes have bailed on you, who's left?

That's the question Rudy is likely to be asking as the story gets bigger and bigger. And the answers won't be pretty, because the rats are going to flee this sinking ship. And finally, in a week or two, Rudy is going to have to decide whether he wants to pull out before Iowa, and save what little dignity he has remaining, or risk polling below Ron Paul in every primary.

But tonight, at least, for two hours in St. Petersburg, Rudy can pretend that he's still a frontrunner for the Republican nomination. No one will be asking him about his greatest fear. He'll get to talk about 9/11 and taxes and Iraq and all that stuff he loves so much. And maybe, for just a moment, he'll even be able to forget about the awful fate that awaits him in the spin room. But make no mistake -- no matter how polished and presidential he looks on that stage tonight, Rudy Giuliani's days as a serious contender are almost certainly over. He's a dead man debating.