You can do that, but if you're in a state where you can vote for Obama, that's the way to go.
The GOP nom is going down to Romney v. McCain, and Romney is going to prevail. If you're in a competitive Super Tuesday state, go with your instinct as stated. If you're anywhere else, go Obama.
Why? Because Romney-Thompson v. Obama-Whoever in Nov.? Foggedaboudit.
I think Hillary is more beatable than Obama.