Here are some results from the last four elections showing the Democratic vote percentages in Ohio vs the national totals.
Only once did the Democratic candidate outperform in Ohio compared to the national vote, Kerry in 2004, and only by 0.4%. Right now the RCP poll averages are showing Romney ahead nationally by 1% and losing Ohio by 1.3%. This result is highly unlikely, as it represents a swing of 2.3% in Obama's favor in Ohio, a clear outlier. If Romney is winning nationally, I expect him to win Ohio by about a half to full point more. Ohio is a swing state because it is representative of the country as a whole in its mix of urban, suburban, rural, white and non-white voters. I put more credibility in the national polls than the state polling, so I have to believe that Romney is actually ahead in Ohio. As a result, here is where I think the map stands today.
My map is almost identical to Silver's "nowcast" with the exception that I have Ohio in the Romney column.
Sean Trende spends three pages to come to the conclusion that Ohio (or whichever state puts Romney over the top) will follow the national trend.
The tendency over the course of this cycle has been for the popular vote in the states to trend toward the national vote. Given this tendency, and the overall history of the Electoral College, the smart money suggests that these state polls will revert to a mean somewhere around the popular vote in relatively short order.