All summer, as John McCain has chipped away at Barack Obama's lead in national polls, Democrats have consoled themselves with the thought that no matter how close it got, Obama was still ahead.

Maybe not anymore.

A new Reuters/Zogby poll out Wednesday showed McCain leading for the first time this campaign, 46-41, among likely voters. It was taken from Thursday through Saturday, while Obama finished up his vacation in Hawaii and after McCain had spent a week talking incessantly about the crisis in Georgia. When the poll was taken a month ago, Obama led by 4 points. "There is no doubt the campaign to discredit Obama is paying off for McCain right now," pollster John Zogby said. "This is a significant ebb for Obama."

Republicans had been saying for months that if they could keep it close going into the conventions, they'd be in good shape. This is probably better news for the GOP than it expected. Before they start cracking the champagne at McCain's suburban Virginia headquarters, though, it's important to note that figuring out who "likely voters" are this year has been giving pollsters heartburn. It's possible this poll's model undercounts support for Obama by discarding people who haven't been reliable voters in the past, but will definitely show up in November. And of course, this is Zogby -- he has been wrong before (and, like all pollsters, he'll probably be wrong again).

But there's no question the race has tightened up a lot, and Obama's going to need to figure out a way to recover some of his momentum -- and stop McCain's -- before too long.