According to all the overnight polls below, voters chose Obama as the winner. But why?

My theory is that The Real McCain finally came across: angry, cocky, belligerent, and snide. Even though McCain is famous among Senators for his rage, he normally goes to extraordinary lengths to keep his anger out of public view by covering it with his forced and creepy smile. But last night he forgot his smile and let just enough of his anger and contempt loose to turn people off. He certainly lost Chris Matthews:

So why did McCain fail to conceal his anger and contempt? Was it because he's terrified about trailing in the polls and losing ground? Or because he really is contemptuous of Barack Obama? I suspect it's more the latter. And I suspect he simply hates Obama because he (a) is smarter, (b) more charming, (c) didn't spend 6 years suffering in a POW camp, (d) has a truly loving family, and (e) is black.

(Psychiatrists and primate behavior specialists are offering another explanation: that McCain is afraid of Obama, so he refused to look at him to avoid reinforcing his fear. So while McCain's attitude might not be actual contempt, that's the impression he conveyed by refusing to look at him.)

Whatever the reasons, The Real McCain may be an effective debater, but he's not appealing. And he's certainly not the guy you'd rather have a beer with because you'd probably end up with a broken jaw.

CBS: Obama won 39% to John McCain's 25% with 36% saying the debate was a draw.

Nearly half of those uncommitted voters who watched the debate said that their image of Obama changed for the better as a result. Just eight percent say their opinion of Obama got worse, and 46 percent reported no change in their opinions.

McCain saw less improvement in his image. Thirty-two percent have improved their image of McCain as a result of the debate, but 21 percent said their views of him are now worse than before.

Why did voters' image of Obama improve? Many volunteered that they were impressed by his poise and knowledge about the issues, that he was more knowledgeable about the issues than they thought previously. When it came to McCain, those same voters said he "didn’t control himself well under pressure," that he was "angry and bad-tempered," and that he "talked too much about the past."

CNN

Men were nearly evenly split between the two candidates, with 46 percent giving the win to McCain and 43 percent to Obama. But women voters tended to give Obama higher marks, with 59 percent calling him the night's winner, while just 31 percent said McCain won

Nate Silver:

TPM has the internals of the CNN poll of debate-watchers, which had Obama winning overall by a margin of 51-38. The poll suggests that Obama is opening up a gap on connectedness, while closing a gap on readiness.

Specifically, by a 62-32 margin, voters thought that Obama was "more in touch with the needs and problems of people like you". This is a gap that has no doubt grown because of the financial crisis of recent days. But it also grew because Obama was actually speaking to middle class voters. Per the transcript, McCain never once mentioned the phrase "middle class" (Obama did so three times). And Obama’s eye contact was directly with the camera, i.e. the voters at home. McCain seemed to be speaking literally to the people in the room in Mississippi, but figuratively to the punditry. It is no surprise that a small majority of pundits seemed to have thought that McCain won, even when the polls indicated otherwise; the pundits were his target audience.

More Nate Silver:

The CBS poll of undecideds has more confirmatory detail. Obama went from a +18 on "understanding your needs and problems" before the debate to a +56 (!) afterward. And he went from a -9 on "prepared to be president" to a +21.

Stan Greenberg/Democracy Corps:

Of our 45 initial undecided voters, a quarter moved to Obama and a quarter to McCain after the debate with the rest remaining undecided. Moreover, by a 38 to 27 percent margin these voters said that Obama won this debate.

A look at the underlying numbers shows that Obama made important gains that could endure through Election Day. These undecided voters had a strong positive reaction to Obama on a personal level. Before the debate, just 40 percent viewed Obama positively, but this skyrocketed to 69 percent after the debate – a remarkable 29-point gain that left him more personally popular than McCain despite this group’s conservative leanings. He also made large strides on being seen as independent, from 44 percent to 65 percent. And in head-to-head matchups against McCain, Obama made significant gains on who "shares your values" and is "on your side."

McCain did not fair as well. His personal standing also improved, but not to nearly the same degree as Obama’s. And while he made impressive gains on being a "maverick," he actually lost slight ground on "offering a different path than Bush," showing that these gains were more about style than substance.

Insider Advantage reports those polled Obama won 42% to McCain's 41% with Undecided 17%