Democratic class warfare is usually rich vs. poor.
Ace examines the class warfare - establishment vs. Tea Party, which leads the things like the START treaty passing.
Culture is thicker than ideology. It is often noted by Tea Partiers (and before that, what used to just be called grassroots conservatives before they had a more evocative name) that the leadership class, even the "conservative" parts of the leadership class, shares the same basic culture -- tastes, preferences, religiosity, manners, mods of thought -- with all other members of the leadership class, and that culture is largely liberal in almost all ways.
When offered a choice between their own culture -- shared with liberal senators -- and a culture to them which looks a lot like The Other, alien and frightening, they will do what human beings usually do, behave in a xenophobic, tribal fashion and align with the people they know and respect, and they respect them primarily because they agree with them so much.
Need an answer to the Sarah Palin phenomenon? Look no further.
This I think is the reason many grassroots conservatives hate Mitt Romney and love Sarah Palin. Even though they agree on most issues, they sense Mitt Romney is from that leadership class, and will sell them out at the drop of a hat to keep in the good graces of the culture he admires and identifies with, and Sarah Palin is definitely from their own class -- what the establishment regards as The Barbaric Other -- and will tend to support them.