I swing.
Seriously, I voted for Obama in 2008. I will not in 2012.
I voted Republican in 2008. I will not in 2012. If I thought the GOP had a shot at landsliding the Senate or would have the gumption to eliminate the filibuster, I could hold my nose and vote for Romney to ensure that we get an undivided government that could govern, I would. But I don't see that happening no matter who wins the White House, so neither Romney nor Obama has much chance of getting their domestic policy enacted. That mutes the importance of their differences there as far as I am concerned. Romney has taken positions that would be an absolute disaster for our foreign policy and Obama has proven to be much better on foreign policy these past 3½ years than I thought he would. Probably won't vote Obama either unless none of the third party options meet with my approval. Being better than Romney is not exactly a great reason to vote for Obama, and in any case, no matter who I vote for, South Carolina's 9 electoral votes will be going to Romney.
I normally don't like having the same party control both elected branches of government. When I vote for a democrat for president I almost always support the GOP for house and senate, and vice-versa. Best years we ever had, imho, were when Clinton was president with a Republican house. So normally, if I'm supporting Romney, I'm supporting the democrats in local races.
This year it's sort of different, mostly because I'd like to see a complete repeal of the PPACA. The only way that's possible is with Republicans in control of both chambers and the white house. I'd probably go back to supporting divided government beyond that. Gridlock is good. If they're not passing laws, then they aren't screwing anything up. And that's the best way: government is best that governs least.