Last night's debate between Sarah Palin and Joe Biden may not have "altered the basic contours of the race." But that doesn't mean nothing important happened yesterday. It's just that it was happening 365 miles to the northeast, in the great state of Michigan.

Lost amid all the Beltway blather and bloviation about the Showdown in St. Louis Thursday evening was one of the most significant revelations since the start of the race. John McCain, it seems, has decided to pull out of the Great Lakes State. As Politico's Jonathan Martin reported first, "McCain will go off TV in Michigan, stop dropping mail there and send most of his staff to more competitive states." The information leaked after McCain, who has watched Barack Obama surge to a sizable lead in national and swing state polls over the past few days, canceled a local event scheduled for next week. "It was always a long shot for us to win," said an aide.

That's probably accurate. But the truth is, without Michigan--which the campaign has now all but admitted that it will lose--it's very difficult to see how McCain can emerge victorious on Nov. 4. For months, McCain has made Michigan the centerpiece of his electoral offense, and with good reason. Iowa, a state that George W. Bush won in 2004, is almost certain to swing to Obama; he currently leads there by more than 10 points on average. Same goes for New Mexico, where Obama's ahead by 8. When combined with John Kerry's 251 electoral votes, those two states alone would put Obama within seven of the magic 270 mark; a single, additional win in either Colorado, Virginia, Ohio or Florida--all of which currently favor the Democrat--would put him over the top. Which is why McCain, desperate to make up ground, has long pinned his hopes on Michigan. The Arizona senator was polling within 2 points of his Illinois opponent as recently as Sept. 10.

Unfortunately, the recent avalanche of distressing economic news--especially impactful in a state with the nation's highest level of unemployment--seems to have moved the expensive Great Lakes State out of McCain's reach. The two polls released since Sept. 24--PPP and the Detroit Free Press--show Obama ahead by 10 and 13 points, respectively, and his average lead has more than tripled (from 2 percent to 7 percent) over the past three weeks. McCain's internal polling likely confirms these margins (otherwise, he'd be staying put). As a result, Republican strategists I spoke to last night in St. Louis said that the Republican nominee would now reinvest his Michigan resources in a quartet of Kerry states: Pennsylvania, Wisconsin, Minnesota and New Hampshire. "He could take any one of them," an RNC bigwig told me.

But while the GOP is outwardly optimistic, a closer look at the numbers shows that McCain is no stronger in these states than in Michigan. McCain's strongest pick-up possibility is probably the unpredictable Granite State, where Obama now leads by an average of 4 points but where McCain has a long history of electoral success. Still, the senator would need more than New Hampshire's four electoral votes to make up for likely losses in Iowa and New Mexico--and neither Wisconsin, Minnesota or Pennsylvania is currently leaning his way. In Wisconsin, he trails by 5 points; in Minnesota, he lags by 5.7; and in Pennsylvania, he's behind by nearly 8. According to FiveThirtyEight.com, a site that blends current polling with demographic statistics and past electoral results to generate remarkably accurate Election Day projections--see its primary season record here--the only Kerry state that McCain has a better chance of capturing than Michigan (13 percent) is New Hampshire (37 percent). Pennsylvania, at 14 percent, is a wash; Minnesota and Wisconsin (8 percent each) are probably out of reach.

Ultimately, then, McCain's Michigan withdrawal underscores how limited his electoral map has become. In confirming the news, McCain field director Mike DuHaime was quick to note that the campaign would move staff to Maine, which awards its electoral votes by congressional district. The announcement was revealing. Apparently, the McCain campaign is now staking its path to victory, at least in part, on Obama winning Iowa, New Mexico and Colorado and losing New Hampshire, which would result in a 269-269 draw--at which point McCain would turn to Maine's Second Congressional District (where Kerry won 52-46) for the tie-breaking vote. The problem with this scenario, though, is that's there's no room for error. For Maine to matter, Obama would have to lose his 4-point lead in New Hampshire; his 2-point lead in Ohio; his 3-point lead in Florida; his 0.5-point lead in Nevada; his 0.5 lead in North Carolina; and his 2.4-point lead in Virginia. Not one of them--all of them. Meanwhile, Maine's second district would have to break sharply with the rest of the state, which currently favors Obama by 7.6 percent. Could it happen? Sure. These stats are based on current polling, and as September showed us, voter preferences still fluctuate in response to events. It's just that at this point, Obama has a 7 or 8 plausible paths to 270--and McCain has only one. So for now it doesn't look likely.