Given the choice the Republicans and Democrats in the centre would hugely water down any too left wing proposals. And by too left wing I mean for their standards - not the European one.
In the Senate the democrats still need all 50 of their party to support any legislation just to get it to a tie - that's not going to be easy in itself.
Civil war could be a good laugh though. What are you fighting for? The right to pay thousands for health insurance