These Republicans that will vote for Obama, presumably they are moderate Republicans, right?
Wait... isn't it the social conservatives that have a problem with McCain? If so, who is currently voting for McCain? Could it be the moderate Republicans?
Obama will do very well in the general. I'm not certain if he will cause Republicans to switch. Hell, I'm about as liberal as a Republican can get, always tempted to vote Democratic at every single election. In the end, the cost of the Democratic proposals weighs heavily on me and I vote Republican. That's the way the moderate Republican vote will play out.
The question becomes, what states are battleground states... Ohio, Florida, Pennsylvania, New Hampshire, other rust belt type states, some Mountain west states. All of those are up for grabs, but those aren't the states to watch.
The states to watch are the deep south. Obama crushed Hillary with the black vote and Hucakbee and Romney crushed McCain. If McCain can't convince Southern evangelicals to come out and vote for him, he's done, Obama in an electoral outcome similar to Clinton v. Dole.