Obamacare — as the Affordable Care Act is commonly known — won't be on the ballot next month. But the fate of the eight-year old health care law could be decided by which party wins control of Congress in November.
"Medicare for All" — the progressive alternative to Obamacare — also stands to gain or lose ground.
And the Trump administration will be looking for a green light to keep making health care changes of its own.
Republican strategist Karl Rove wrote about what's at stake in a recent Wall Street Journal column. The headline described health care as the "sleeper issue" of the 2018 midterm elections.
Republican Lou Hendricks agrees. The Kansas City retiree told pollsters health care is at the top of his list as he ponders his midterm vote.
"One of the big concerns that we have as as a family is making sure that there continues to be coverage for previous conditions," Hendricks said.
Sen. Claire McCaskill, D-Mo., who's in a tough battle for re-election, is trying to tap into that concern. McCaskill describes her own struggle with breast cancer in a new campaign ad.
"I don't talk about it much," she says, over video that shows the senator meeting with other women. "Those who faced cancer and many other illnesses have a pre-existing condition when it comes to health coverage."
McCaskill blasts her Republican opponent, Missouri Attorney General Josh Hawley, for joining a lawsuit that seeks to overturn Obamacare and its requirement that insurance companies offer coverage regardless of a person's medical history. Republicans insist they will also protect patients with pre-existing medical conditions, though they've been vague in saying how.
Democrats around the country have seized on this issue. Health care dominates congressional campaign ads, outpacing jobs, taxes, and immigration.
"Democrats have been laser-focused on health care this year," said Erika Franklin Fowler, who tracks campaign ads for the Wesleyan Media Project.
It's the mirror image of past election cycles, when Republicans ran a blitzkrieg of ads attacking Obamacare while Democrats stayed largely quiet.
"Regardless of how Americans feel about the Affordable Care Act, there are provisions of it that are very popular," Franklin said. "Once it became clear that those provisions are in trouble, I think that has sort of changed the landscape of how politicians will talk about it this cycle."
Democrats are determined to protect those popular provisions if they win one or both houses of Congress in November. On the other hand, if Republicans keep control, they could take another run at repealing Obamacare.
"Many Republicans want the ability to finish the job," said Jessica Anderson, vice president of the conservative group Heritage Action. "They've campaigned on this for over eight years."
Anderson said even if Republicans lose in November, they could mount a last-ditch effort to repeal Obamacare during the lame-duck session. The late Sen. John McCain, R-Ariz., who helped torpedo the last repeal effort, has now been replaced by Jon Kyl, a more reliable GOP vote.
No matter which party controls Congress next year, the Trump administration will likely keep trying to chip away at Obamacare. For example, the administration has already relaxed regulations to allow stripped-down insurance policies with reduced coverage.
"The president will still be in office, and his administration will still be active," Anderson said.
But if Democrats win control of either chamber, they might be able to put the brakes on those efforts
"What you're likely to see is much greater and even fierce oversight of the administration's efforts to change — and many would say undermine" the Affordable Care Act, said Drew Altman, president of the Kaiser Family Foundation, a health care research organization.
In Kansas City, Hendricks described himself as a fan of the Affordable Care Act. But more and more he's leaning towards a single-payer insurance system, which progressive advocates like to describe as "Medicare for All."
"It makes it easier and simpler for everybody," Hendricks said, "with he exception of Aetna, Blue Cross/Blue Shield, enter the medical insurance company here."
President Trump has gone on the offensive, claiming without evidence that any expansion of Medicare will come at the expense of today's seniors.
Even if they win a sweeping victory in the midterms, Democrats won't have the power to pass "Medicare for All" over a presidential veto. But they might jump start the conversation ahead of the next election in two years.