Mitt Romney came with a written presentation. Barack Obama came with a seminar outline.

Last night's presidential debate was a study in contrasts, but even more, it was the fulfillment of two wildly held assumptions about the candidates. There's Romney, the business man's business man, so polished that his surface has a way of reflecting whatever scene happens to swirl around him. And there's Obama, the detached philosopher, whose allure has always been his ability to appear coolly separate, even above, the scene around him. So there they were last night, filling out their stereotypes -- one polished, practiced in sound-bites, armed with short lists, making a pitch; the other comprehensive but rarely succinct and, somehow, separate.

Mitt Romney won by ... well, by being Mitt Romney, and Obama lost by being a caricature of his cool distracted professor alter-ego.

A presidential campaign is a year-long decathlon, where candidates have to compete in contests as diverse as fundraising to managing state networks to avoiding gaffes. The evidence from the last 50 years shows that the decathlon -- plus "fundamentals" like foreign affairs and the economy -- matters more than any one televised competition. But even if you discount the power of debates, you shouldn't not count them. These are still 50-million-person theatrical events staged in the final chapter of a razor-thin election. And Romney was clearly the better performer last night. His style shined, both because he came prepared to make digestible points tailored for a moderate TV audience and because Obama did so little to force him off his game plan.

I watched last night's presidential debate out of the corner of my eye. For better or worse, most of my attention was drawn to Twitter, where journalists and wonks agreed, through the use of various sports metaphors, that a focused Romney was giving a lethargic Obama a proper shellacking. Their insta-reaction anticipated the insta-reaction of viewers. A CBS flash poll had Romney winning the debate by a two-to-one margin, 46 percent-22 percent, with the rest calling it a tie. The CNN poll was even more decisive: 67 percent gave it to Romney, which is reportedly the widest victory in CNN post-debate history.

THE TRIUMPH OF VAGUENESS

Last night was a victory for Romney's style, but it was also a small vindication of his strategic pursuit of vagueness. His debate plan was ostensibly to be as specific about Obama's plan as he was unspecific about his own. And it worked.

For months, the press has encouraged Romney to be more specific. His tax plan, for example, isn't a document, but rather a list of principles. The only thing we know about his immense budget cuts is what he's promised not to cut (and it is a list so long it makes you wonder whether unemployment insurance will eventually have to run on donations). But Romney steadfastly resisted the specific, and for at least one night, it paid off. Asked if he would cut taxes for the rich, Romney said no. Pressed if he would raise taxes on the middle class, he said no. Roll back regulation? Not if it's smart regulation. Cut education? Of course not. Slash critical investments in America's future? Heck no.

If Obama had been better prepared for Romney's agility, he might have pointed out that all of these things can't be true at the same time. You cannot cut tax rates the way Romney would like without: giving the rich a break; raising taxes on the middle class; increasing the deficit; or slashing the most sacred tax provisions in the law. Romney can't say his tax plan would avoid all four outcomes, because any plan that avoids all four outcomes is not his tax plan. Furthermore, without higher revenue or cuts to defense, Social Security and Medicare, Romney's deficit-reduction schedule explicitly requires deep cuts to low-income support programs and/or basic government investment in roads and research.

One big reason Romney succeeded because he found a way to make promises to a mainstream TV audience that didn't appear to shatter his former promises to conservatives. One big reason Obama lost was because he failed to point this out.

ENTITLEMENTS

"Mr. President, you're entitled to your own airplane and to your own house, but not to your own facts," Romney quipped toward the end of the night. In fact, both candidates acted as if they were entitled to their own facts, especially about entitlements. Obama characterized Romney's tax plan as a $5 trillion cut, which ignores the governor's promises to find offsets. This is more or less as unfair as Romney's repeated claim that repealing Obama's "government takeover" of health care would reduce the deficit, since Obamacare offset its higher spending with taxes.

I didn't hear any new whoppers last night, just the same old (and very wonky) fibs. Last night wasn't a breakthrough for substance so much as a predictable, if too in-the-weeds, performance off two predictable scripts. Romney was, by far, the superior showman. His best hope is that enough undecided voters tuned in to see the capable executive Republicans have been hoping for. Obama's best hope is that his energy level caused enough Americans to feel too tired to make an executive decision.

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Update/Compare and contrast: Ezra Klein came to a very similar conclusion about vagueness boosting Romney, and Phillip Klein came to the opposite conclusion.