I have noticed that Republicans seem to be rather self centered. Very rarely do they put cause ahead of personal ambition, unlike Democrats. See NJ 2002 and MO 2012 for two prime examples from each side.
It's pretty simple. Audacious Epigone pointed out that liberals, as diverse as they are, are basically a "hive minds" on issues and how to win. Conservatives, on the other hand, were described ideologically as "a herd of cats", with a whole host of different philosophies, objectives, and strategies. I don't know if he's completely right, but the Dems are far more disciplined.
