“I think it’s an opportunity to reset with the new year to remind people that there’s a very real threat to tens of millions of Americans," Sen. Brian Schatz (D-Hawaii) said in an interview. "We Democrats are always striving to improve the system, but, at a minimum, the American people expect us to protect what they already have."

In 2018, Democrats won the House majority and several governorships largely on a message of protecting Obamacare and its popular protections for preexisting conditions. This year continued the trend, with Kentucky’s staunchly anti-Obamacare governor, Matt Bevin, losing to Democratic now-Gov. Andy Beshear.

The landscape in 2020 may be more challenging for Democrats than it was in 2018, when Republicans had more recently voted to repeal the Affordable Care Act. Republicans also say they now have more ammunition to push back on Democrats’ arguments with the party’s divisions over single-payer health care, which would replace Obamacare, shaping the presidential race.

Moreover, the appeals court's ruling — which in all likelihood punted any final disposition on the case until after the 2020 elections — eliminates what some Republicans saw as a nightmare scenario: If the court had embraced a lower court ruling striking down the law in its entirety, it would have put the issue before the Supreme Court during the heat of the election, putting tens of millions of Americans' health insurance at risk.

Still, Democrats believe they can win the political battle over health care, especially in Senate races. At least a half-dozen GOP senators are up for reelection, and Democrats need to net three seats to win back control of the chamber if they also win back the presidency. Democratic strategists and candidates are eager to run a health care playbook that mirrors that of the party’s House takeover in 2018, and say Republicans are uniquely vulnerable after admitting this year that they have no real plan for dealing with the potential fallout of courts striking down Obamacare.

Within a day of the ruling, the pro-Obamacare advocacy group Protect Our Care cut a national TV and digital ad featuring images of Sens. Susan Collins (R-Maine) and Cory Gardner (R-Colo.), warning that if the lawsuit succeeds, “135 million Americans with preexisting conditions will be stripped of protections, 20 million Americans will lose coverage and costs will go up for millions more.”

Other state-based progressive groups told POLITICO they’re readying their own ads going after individual Senate Republicans over the 5th Circuit’s ruling.

Protect Our Care director Brad Woodhouse predicts that it’s just a preview of the wave of attention the issue will get in the months ahead, as Democratic candidates and outside groups alike hammer the GOP on the threat their lawsuit poses to Obamacare.

“If there is one issue in American politics that is going to flip the Senate from Republican to Democratic in 2020, it’s this issue,” he said. “Our message is simple: President [Donald] Trump and Republicans are in court right now, suing to take away the ACA, take away your health care. And if Cory Gardner or Thom Tillis or any of them don’t think that’s an indefensible position, they should ask the 40-plus House Republicans who lost their seats in 2018.”

More than a dozen Republican state attorneys general, backed by the Trump administration, have been arguing in federal court for more than a year that Congress rendered the entire Affordable Care Act untenable when they voted as part of the 2017 tax bill to drop the penalty for not buying insurance down to zero. A district judge in Texas sided with them last year in a sweeping ruling declaring all of Obamacare unconstitutional.

Last week, an appeals court agreed that the elimination of the penalty made the individual mandate unconstitutional, but sent the case back down to the district court to decide whether any of the law could be separated out and preserved. The move all but guarantees the case won’t reach the Supreme Court until after the election, but it maintains the cloud of uncertainty hanging over the health law that experts say drives up the cost of insurance.

Though no one is in danger of losing their health coverage imminently, Democratic challengers in nearly every Senate battleground race, including Arizona, North Carolina, Maine and Iowa, jumped on the court ruling as an opportunity to attack Republicans on health care.

"Democrats have been in the fight to ensure that people across this country have access to affordable health care," said Sen. Catherine Cortez Masto of Nevada, the chair of the DSCC. "This opinion does not help the Republicans.”

Sara Gideon, Democrats’ preferred candidate in Maine to take on Collins, called the lawsuit a “direct threat to the protections countless Mainers and Americans depend on. She has been reminding voters that Collins’ vote on the 2017 tax reform law triggered the ACA lawsuit in the first place, and she voted to confirm one of the 5th Circuit judges that recently sided with the Trump administration’s arguments against the law.

Unlike the vast majority of her GOP colleagues in the upper chamber, Collins has spoken up against the lawsuit. She has written multiple times to Attorney General Bill Bar, urging him to defend the ACA in court. Collins told POLITICO the day after the ruling that it was “significant” that the 5th Circuit judges were clearly “very uneasy with the thought of striking down the entire law” and instead sent the case back down to the lower court for reconsideration. Collins’ campaign spokesman both emphasized that she believes the government should defend the law and criticized Democrats for defending the unpopular individual mandate.

Tillis, the vulnerable North Carolina senator, said the lawsuit gave Republicans “breathing room” to find a viable replacement for Obamacare and attempted to flip the attack on Democrats by tying them to their presidential contenders.

“I think the fact that they all raised their hands and said we need Medicare for All is also raising their hands and saying the Affordable Care Act has failed,” Tillis said.

Though most of the 2020 presidential candidates have come out against Medicare for All, and more Democratic voters favor a choice between private insurance and a public option, the single-payer debate has given Republicans a potent line of attack that they’re turning to more than ever in the wake of the court’s ruling.

“Obamacare failed to lower health care costs for millions of Americans, and now Democrats want a complete government takeover of our health care system,” said Jesse Hunt, a spokesman for the National Republican Senatorial Committee. “They spent all of 2019 defending their socialist plan to eliminate employer-based health care coverage, and those problems will not subside anytime soon.”

The effectiveness of the GOP attacks will depend largely on the Democratic nominee for president — if it is someone who backs Medicare for All, it will be much more difficult for Senate candidates who don’t support the policy to separate themselves from it. But Democratic activists say they're confident the GOP’s actions in court will sway voters more than their claims about Medicare for All.

“We can prepare for and counter those attacks by reminding voters that [Republicans are] fighting actively to take health care away,” said Kelly Dietrich, the founder and CEO of the National Democratic Training Committee, which coached more than 17,000 candidates for federal and state office in 2019. “Republicans' ability to use fear as a tool to win elections should never be underestimated. But the antidote is to fight back just as hard.”