UPDATE: 10/04 @ 11:40 AM
Now that the Common Wisdom on the first debate was that Kerry one, Bush partisans are switching tactics. Now they are quietly admitted that Kerry might have won (or that it was a "draw," which means Kerry won), but they argue that Kerry needed a knockout to really move in the election (examples here and here). I'd be tempted to dismiss this as normal spin, but because it has a chance to become a conservative talking point in the media, I feel compelled to address it. Kerry didn't need to blow Bush out of the water. He just needed to be a viable alternative.
John Kerry's problem has never been convincing swing voters that George Bush is doing a bad job. They're already well aware of that. Indeed, only 16% to 20% of undecided voters feel that the President deserves to be re-elected, while forty-percent of them feel that it is time for someone new (and that was before the debate!). Kerry's problem is that voters didn't see him as a viable alternative. They were worried he was spineless, a flipflopper, someone who would outsource our foreign policy to Paris. All John Kerry had to do was prove he wasn't a total wimp, and he'd convince alot of people who don't like Bush but weren't sure of the alternative.
The latest Newsweek poll confirms that this was the effect. Not only did Kerry erase his deficit, but he improved vis a vis Bush in virtually every category, jumping 6 percent in intelligence, 6% in leadership, 5% in ability to handle an international crisis, and a 12 point net gain on Homeland Security, among others. Bush's overall approval rating has dropped to 46%, the same amount of people who want to see him re-elected. (the CNN/Gallup poll says essentially the same thing). In other words, now that Kerry's proven himself not to be a total sap on these issues, he can persuade the plurality of Americans who'd rather see Bush out of office that they can trust him to be in it.
UPDATE: I finally found the bombshell support article for this proposition, from The American Prospect. If you're a Kerry partisan and want to be encouraged, check it out.