The GOP will go all-in in their efforts to make the entire election some kind of referendum on the ACA - as if the 2012 Obama landslide was a fantasy - and the Dems will do their best to fight the health care issue to a draw.
The thing is, the Republicans have absolutely no credibility when it comes to health care as an issue. Aside from motivating the GOP base, anti-ACA rhetoric doesn’t translate into more rightwing voters. The public doesn’t like Ocare, but they like what’s in it and they don’t want to see it repealed. Repeal is such an impossibility anyway, that I honestly don’t know if the Pubbies even believe it themselves at this point.
The Dems will run on a minimum wage increase, immigration reform, income inequality, etc.
At this point, I don’t think the Dems have any chance of retaking the House, though they might increase their numbers in that chamber. Nor do I think that they’ll lose the Senate, although their majority will slim up a bit.
At least in terms of the Senate, though, my prognostications can change up until the election. Come back to me in September.