President Obama’s achilles heel in this election is his performance with white voters. If he falls below 40 percent, his prospects for reelection are endangered. Given the tight race Iowa, and the seemingly tight race in Michigan, one theory is that Obama has slipped below the critical mark for white support. It’s part of the reason the Romney campaign is loudly touting its efforts to “expand” the electoral map and put President Obama on the defensive in several key states. To wit, the Restore Our Future Super PAC has launched a $1.8 million ad buy in Minnesota and New Mexico — two relatively safe states for Obama — and the Romney campaign itself has made moves in Pennsylvania, Michigan, and Wisconsin.

Unfortunately for Team Romney, a poll released this afternoon, from Marquette Law School, throws a little water on this theory. In Wisconsin, Marquette — one of the most reputable pollsters in the state — shows Obama with an 8 point lead over Romney, 51 percent to 43 percent.

Still, this is only one poll, and others show a closer race in core Democratic states. A Detroit News poll has Obama with just a 3 point advantage in Michigan (48–45), a Mason-Dixon poll has him with a similar advantage in Minnesota (47–44), and a Pennsylvania poll from Franklin & Marshall shows Obama ahead by 4 points (49–45) in a state that he won by double-digits in 2008.

If these polls are an accurate picture of the race, then we’re looking at a fundamental shift in the election. A world where Obama is falling behind in blue states like Michigan and Minnesota is one where his support among white voters is actually collapsing.

But judging from the polling averages, Marquette — which implies steady performance with white voters — seems generally closer to the mark. In states with similar demographics to Wisconsin, Obama is still leading. In In Minnesota, Obama has a 6.9 point lead over Romney; in Michigan, it’s also 6.9 points; in Pennsylvania, it’s 4.9 points; and in Wisconsin, it’s 4 points, with Obama breaking 50 percent.

As with last week’s “momentum” narrative, Team Romney’s declaration that they are “expanding the map” has more to do with perception than reality. Barring something catastrophic, there’s no way Romney can close the gap in Minnesota or Michigan. Indeed, far from showing confidence, Romney is revealing the extent to which he’s worried about his path to 270 electoral votes.

The most valuable state on the board is Ohio, Without it, Romney has to run the table everywhere to win the presidency. And so far in the state, Obama has maintained a small but resilient advantage — a 2.4 point lead according to the Pollster average, and an identical one in the Real Clear Politics average. Doing something as simple as taking a median of the most recent polls — which drops the outliers from consideration — leaves you with an Obama lead of 2.5 points.

If Romney had leads in Virginia and Colorado, things would look a little different, but he doesn’t. The contest in both states is a dead heat. Romney is aching for a secure path to the presidency, and his push to “expand the map” is a clear sign he doesn’t have one.

Jamelle Bouie is a staff writer at The American Prospect , where he writes a blog .