Irrelevant small states with no people in them that exist by an accident of history are chronically over-represented in this country — both in the electoral college and most obviously in the Senate. And those states are much more conservative than metro areas where people actually live, which means that even if they send Democrats to DC, they’re not exactly raging Trotskyites.
Hence we get Max Baucus, representing less than 1 million people, or one-sixth of an average state’s population, pushing moderate reform and saying that single-payer is a political non-starter. He’s right, but it’s only because of the political structure that guarantees him his power. If San Francisco, which has roughly the same population as Montana, sent a Senator to Congress I think the result would be somewhat different.