Is this a reasonable strategy for how Democrats can expand social programs in our times?
(1) When Republicans are in power and decide they want to pass a bloated and ill-designed domestic program without paying for it, vote with them so it passes. (See: Medicare Part D.)
(2) When you're in power and you decide that you want to pass a well-designed program that will cost some money while reaping the supposed political benefits of being deficit-neutral, suck some of the money out of the bloated program and use it to pay for your thing. (See: Affordable Care Act.)
As Ezra points out, Democrats didn't see any big political benefits from the ACA reducing the deficit. Maybe the successors of the defeated Blue Dogs won't care so much about deficit stuff and we won't bother with paying for stuff next time around. But if we have to, is this a reasonable plan?