The categorization is somewhat...suspect. This is from the latest tweets "for Romney".
- hate Americans who are like 'I always vote republican so of course I voted for romney'
- I'm not afraid to say who I voted for. I voted for Obama cause lets face it, Romney's just a dickhead.
- Sweet satire. "Why I voted for Mitt Romney" http://www.salon.com/2012/11/06/why_i_voted_for_mitt_romney/....
That said, from polls we know that the overall vote is going to be very close to 50/50, so the lopsided totals are a sign of skew in Twitter users, not the country.