Without the Democrats there'd be no tea party movement. People were angry at Bush and the Republicans and that anger carried over to the Democrats when they did the same things on steroids. Had the Democrats been smart they would've talked to their constituents and attempted to deal with their concerns. Instead the Democrats insulted and berated these constituents again again and again.
Being treated like you're bull dung will motivate you far more than the things you object to. The Democrats seemed to be making a conscious decision to get the tea party people to hate them. As a result, they end up working a lot harder to unseat them. Say what you want about Republicans, but they save their negativity for their congressional opponents. I can't see a benefit toward treating voters this way. Maybe they want a book titled, "How to Create Enemies and Motivate Them to Work Against You."