Conservatives say they want the "Bush tax cuts" extended because they think it will help the economy. But if Obama signs off on an extension and the cuts have the effect they expect, won't that help Obama get reelected? Come 2012 he can say he cut everyone's taxes and made the economy better off. He won't even have to say that because people will see the effects themselves, that is, according to the logic of extending them.
So why not let them expire, let the economy drag along, bring in more revenue to help with the deficit, and increase your chances of getting rid of the socialist abomination that is Obama. Then you get your person in, cut taxes, the economy booms and you have at least another 8 years of true capitalism and a restoration of liberty.
If the GOP really believed what their ideology tells them on tax cuts they should be calling for all of the cuts to expire. After all, isn't getting rid of Obama more important to them than cutting taxes for a few years?