In name only. Munchkin (from WV) did NOT vote to support Dem policies. He voted AGAINST.

Not in name only. Manchin was a Democrat. He was a conservative Democrat, but a Democrat nonetheless. Plus, in 2008 Manchin wasn't necessary to the Democratic majority in the Senate - they had 58+ seats.

The reason that Democrats can't enact their promises on climate and health care are the same reasons why the GOP can't enact their promises on the budget. Even though the parties claim that it's possible to achieve their agenda with no pain to anyone (except the folks who deserve that pain), it's simply not true.

So when they actually have to go out and get votes, various portions of their coalition balk - because the proposals will end up hurting some of their constituents, and they don't want to do that. It isn't a win-win. You can't materially cut taxes and keep current government services without piling up the deficit - there just isn't enough money being wasted to make the math work. You can't switch to single-payer health care without making most people pay more or slashing health care worker compensation - there just isn't enough money being wasted in private insurance to make the math work. Etc.