Self-interest, my friend. There is not a human behavior (or behavior of any organism, really) that cannot be traced back in some way to self-interest. Altruism almost never makes sense biologically... You can thank the Green Party (and Ralph Nader) for having Bush here in the first place. Our Electoral System was designed before the advent of American political parties. As a result, third party candidates have no chance of being elected, and at best can simply be 'spoilers,' which is what Nader was in 2000...taking away votes from Gore, likely allowing Bush to take Florida. A strong 3rd party could come into play eventually, but it would have to originate at the local or state level around the country simultaneously and win a large number of seats in Congress before it had a chance to win. Yeah, it's all screwed up, but you have to realize that 217 years ago The American Experiment in self-government was a novel idea and expected to fail throughout the world. They had really nothing to base it on, and were rightfully leery of trusting the people with too much power.