Throughout the duration of the 2018 campaign, health care was the key issue for voters and the key issue for Democrats. It gave them the House of Representatives with a net gain of 33 seats and the chance of even more gains with eight races still uncalled. They are going to take that healthcare mandate and run with it through 2020.
One of the first orders of business will be to determine how to intervene in the challenge 20 states have brought against the Affordable Care Act. With the Trump administration not only refusing to defend the law but actually joining in the suit arguing that the law's protections for patients should be struck down, the House Democrats are considering the best way to join the Democratic states' attorneys general in defending it.
They're also looking at means of shoring up the law, "stabilizing the Affordable Care Act marketplace, controlling prescription drug prices and investigating Trump administration actions that undermine the health care law." Along with providing a legal defense for the law, they're looking at early legislation to ensure people with pre-existing conditions will keep the protections in the ACA, the number one issue of 2018, and put Republicans who joined that bandwagon during the campaign on the spot.
Given the number of seats the Senate Republicans have to defend in 2020, that's a smart move. They saw the bloodbath that was the House in addition to three very red states voting to expand Medicaid, so many will want to try to erase the Democratic advantage on the issue. At the same time, there will always be the handful of extremists—Ted Cruz who is returning, Tom Cotton, Ron Johnson, et al.—clamoring for repeal. That's the kind of pressure Democrats need to put on Mitch McConnell.
The Trump administration isn't likely to be doing Republicans any favors here. At this point, it intends to keep up Trump's efforts at undermining the law and kicking people off of Medicaid. Senate Republicans are going to be trapped between the House Democrats pushing to save people's health care and Trump trying to take it away. It could be enough to force McConnell into compromise with the House.