In the united states 2012 national elections who do you want to win? regardless of nationality and how do you think it would affect bitcoins as a currency?
Neither is more likely to make an impact on Bitcoin than the other. The most likely thing to make the US government pay attention to Bitcoin is how it can be abused. There are dozens, maybe hundreds of mixers, and they're prime targets for people that are doing less-than-legal things. If the US government decides that Bitcoin is a vector for drugs or terrorism, things could get rather messy. Neither of the two major candidates have policies that would make this scenario more or less likely to happen.