That's because Republicans aren't as much of a threat to their office as progressives. Some Dems are sitting in basically lifetime seats and they wouldn't want that disrupted. The Ds haven't done anything significant yet at all. And it won't come from Democrats. It'll come from the people if it happens at all. And once something big happens by and from the people, that's when the Ds will step in and take a side. Fucking cowards.