Both the Democrat and Republican parties are considered by the new breed of "progressive-liberals" as "corporatist," "fascist" and "pro-war." True enough. So some of them ask, "why bother voting?"
Answer: Because voter apathy is one of the most powerful weapons in any politician's arsenal. If the other side adopts a "why bother" attitude and fail to show up at the polls, it gives them an even greater opportunity to win. And once they win, so will their policies. And once their policies are firmly in place, it's hell trying to get them undone.
Others ask "why not show you're pissed at both parties by voting a third-party candidate?"
Answer: Because every time dissatisfied liberal voters gave the bird to their liberal candidate by voting third-party, the conservatives end up winning. I don't want to bring up the "spoiler" cliche, but there's a reason why it exists.
And a lot of these "progressive-liberals" are now asking "why can't we field a primary challenge against him, so we can force him into being more liberal / put a real liberal in office / show everyone how positively pissed we are?"
Answer: Internecine fighting makes it all the more possible that come January 2013, you'll be seeing President Rick Perry being sworn in.