I looked at Mitt Romney's swing state v. national performance two weeks ago, before the debate, finding that Romney actually improved by more in the average swing state than in the national poll. At the time, President Obama led by 3.7 points. Now the election has moved more than 5 points toward Mitt Romney, with the former Massachusetts governor leading by 1.4 points in the RCP average.
Mitt Romney led in no swing states on October 1. He leads in North Carolina, Florida, and Colorado now. Yet that'd still give a 294-244 electoral college loss. What gives?
As the above chart shows, Romney has gained dramatically in swing states, although not by as much as he has nationally. Now, he's running 8.7% ahead of McCain nationally and 7.9% in swing states. Of course, all swings won't be the same. If he was getting an 8.7% swing in all swing states, he would add Virginia and Ohio, but not Colorado. He'd still lose 272-266. Still, the average gain isn't too dissimilar to the national gain. He won't necessarily gain the same in swing states as he does nationally.
The above chart projects out state by state vote based on margins and projected turn-out. Barack Obama leads by 1.8% if we look at all the state polls. That's incongruous with a Mitt Romney lead of 1.4%. This makes more sense when we realize that the numbers used for the above chart include 15 red states and 8 blue states which haven't been polled since the debate. If those states were adjusted based on expected post debate swing Romney would lead by 0.4%. That's still 1.0% behind his national number but such a variance could easily be explained by different pollsters, different days, and even that a poll that has Romney ahead by 2 points is actually 1.7.
Romney's average move of 7.9% in the swing states is below his aggregate move of 7.2%, because his move is larger with small states than bigger ones like Pennsylvania, Ohio, and Florida. Even so, he's around 50%-50% in swing states. Because they haven't been polled lately, or as often, Mitt Romney isn't gaining as much in the red and blue states as he is in the swing states. Again, however, that probably wouldn't be the case if there were more recent polling data for many of them.
Thus, we can't assume that Mitt Romney winning the popular vote will mean an electoral college win. It's likely it will, but wouldn't be inconsistent if he didn't.