Nate Cohn has a TNR post that underscores the pivotal importance of President Obama getting a bigger portion of the white working class than recent polls have indicated to secure key swing states. Cohn links his analysis to a “best fit” chart revealing the relationship between current polling averages in a dozen ‘battleground states’ and the percentage of working class voters who supported Obama in ’08. As Cohn explains:

…Beneath the chaos, there is a discernible organizing principle: Obama has fallen furthest in the states where he accrued the most white and particularly white working class support in 2008.
State and national polls have long shown that Obama’s already tepid support among white voters without a college degree has collapsed. At the same time, the “newer” elements of the Democratic coalition–college educated and non-white voters–have continued to offer elevated levels of support to the president. And predictably, the imbalanced collapse of Obama’s once broad coalition has rejiggered the electoral map.
The correlation is pretty clear, but keep in mind that these numbers are driven by relatively few data points. Changing just a couple of the polls can make or break the relationship: Simply excluding the recent WAA poll in Virginia, for instance, moves that state directly over the best-fit line. I’d also note that there is a similar correlation with white voters, except that the slope of the best-fit line is not nearly as steep, since college educated white voters haven’t moved as decisively against Obama. But overall, it’s a convincing explanation of recent shifts in the electoral map.

Cohn adds that the correlation “might not hold until Election Day,” particularly if Obama improves his polling approvals with white workers in IA, MI and WI. For now, however, “…the imbalanced collapse of Obama’s coalition has redefined the electoral map, leaving Obama embattled in white working class Midwestern states but relatively well-positioned in the diverse “new coalition” states of the Mid-Atlantic and Southwest.”