Atrios is succinct and spot on here. Certain Democrats can start running from the ACA like cowards but it won’t help them.
Whatever the merits of ACA, it is now something the Dems own. For decades I’ve watched Dems try to run away from things which have been surgically implanted on any politician with a D next to their name. It’s always bizarre and pointless. You’re the party of gay marriage, abortion, and Obamacare whether you like it or not, and it’s better to convince your constituents that you’re going to do good things for them than to try to convince them that you’re not a real Democrat.
They can already vote for someone who isn’t a real Democrat. He or she is called a Republican.
The right argument for them to make is that big fundamental changes are hard and almost always start out bumpy. There was a day when not one American had a Social Security number, now they all do. ACA is big like that.