Nate Silver at 538 helpfully points out that the real division over today's failed bailout bill wasn't party; it was career. Among members of Congress from safe districts, the vote was essentially 50-50. However, members from competitive districts opposed the bill 30-8. Moreover, members who are retiring supported the bill 23-2-1.
This is not terribly surprising. If you're facing a tough re-election fight, and a president with a 28% approval rating tells you to eat a shit sandwich, and your constituents know it's a shit sandwich, it's pretty obvious where your loyalties lie.