Unemployment rates in key swing states are much lower than the national average (with the exception of Florida, Nevada, and North Carolina). Tom Holbrook makes the case that "presidential elections are national elections and it is national conditions–not state-level variation around those conditions–that drive them":
[I]t may seem natural to expect that voters living in states with more rapidly improving economies would be more likely than voters who live in states with weaker economies to support incumbent party candidates. It also makes sense that so much attention has been paid to the unemployment rates in the states, given the overall high levels of unemployment. However, I did some work on this a long time ago (dissertation, actually) and found that what appeared to be state-level economic effects in a pooled vote model vanished in the presence of controls for the state of the national economy. And even though others (see Campbell and Klarner) have found significant state-level economic effects in more recent pooled models that used broad indicators such as change in income and change in economic output, I'm still skeptical that state-to-state variations in economic conditions–especially those based on unemployment–have much to do with presidential election outcomes.
The Dish 