CHELSEA, Mich. ― People who depend on the Affordable Care Act’s protections for people with pre-existing conditions have a great deal at stake in Tuesday’s elections. But so do people who rely on Medicaid, even though they’ve gotten a lot less attention this election cycle.

Aaron Robertson is one of those people. Robertson, 35, lives in Chelsea, Michigan, a city of roughly 5,000 people that’s about an hour’s drive west of Detroit. He works in a downtown coffee shop, making enough money to support himself but not enough to buy health insurance. He went without coverage for many years until 2015, when he signed up for Michigan’s version of Medicaid.

The timing was fortuitous, because just a few months later, while helping his uncle perform some maintenance on a boat, he slipped off a 12-foot ladder and shattered several bones in his foot. The treatment would eventually involve two separate surgeries, plus months of rehabilitation.

It was painful, except in the financial sense. Medicaid took care of bills, leaving him with only a handful of out-of-pocket expenses.

“I was lucky,” Robertson told me during a recent interview, on a rainy evening just days before the election. Without Medicaid, he figures, he would have ended up bankrupt and maybe permanently disabled, because he would have skipped follow-up care and probably the second surgery, even though the first procedure didn’t fully repair the damage.

“I probably couldn’t work, I’m not sure what I would have done,” Robertson said. “How can you afford anything if you can’t work?”

HUFFPOST PHOTO/Jonathan Cohn Aaron Robertson enrolled in Medicaid when Michigan expanded the program and, shortly afterwards, he shattered his foot. “I’m really hoping they don’t take it away,” he says. “That would hurt a lot of people."

Robertson was able to get on Medicaid because Michigan is one of 33 states that, along with the District of Columbia, has decided to take part in the ACA’s expansion of the program.

That means the states have opened up their Medicaid programs to anybody with income below or just above the poverty line, instead of restricting enrollment to narrowly defined groups like children, pregnant women and people with disabilities. The federal government picks up most of the cost.

The effects have been dramatic. More than 680,000 Michiganders have gotten coverage through the expansion, according to official estimates. And that’s emblematic of what’s happened across the country.

Overall, roughly 14 million people got insurance because of the Medicaid expansion, and that is the single biggest reason that the number of people without coverage has fallen to historic lows since the ACA took effect.

But those gains could vanish, depending on what happens Tuesday.

If Republicans hold onto both houses of Congress, they will almost certainly try once again to repeal the ACA. And if the legislation they consider looks anything like the proposals that they tried to pass last year, it will both eliminate the extra federal funding for the Medicaid expansion and ratchet down what the federal government spends on the rest of the program, as well.

Most states would respond by dramatically pulling back on their Medicaid programs, returning eligibility to what it was before the expansion and cutting back on services even for traditional groups like children and the disabled.

As the writer Andrew Sprung put it recently at healthinsurance.org, Republican proposals “could permanently cripple Medicaid.”

An easy way to measure the impact is by looking at the people who would have lost coverage if the American Health Care Act, the repeal bill that House Republicans passed in 2017, had become law. Overall, the Congressional Budget Office concluded, the number of people on Medicaid would have fallen by 14 million, effectively wiping out the last few years’ gains.

Where Millions Stand To Lose Coverage

That’s a big number, obviously. But it’s a meaningful one too.

A slew of studies, many based on data from the last few years since the expansion has gone into effect, show conclusively that, relative to people with no insurance, people on Medicaid end up better off. That might sound obvious, but it’s actually something that conservative critics of the program, including some with powerful positions in President Donald Trump’s administration, have questioned.

Some of the most recent evidence of Medicaid’s effectiveness happens to come from Michigan, where researchers from the University of Michigan have found that people who got Medicaid coverage were more likely to get cardiac services, for example, and less prone to large credit card debts, evictions and bankruptcy declarations.

Nancy Paul, executive director of Faith in Action in Chelsea, doesn’t need a study to tell her about the expansion’s impact.

"It’s really easy, four or five years into this expansion from the Affordable Care Act, to forget what it was like for people." Nancy Paul, director of Chelsea's Faith in Action organization

For years, her organization worked with a local doctor and nurse to offer basic medical services for the poor. They stopped after the Medicaid expansion took effect because they realized it was no longer necessary. Would-be patients were finding their way to doctors, clinics and hospitals where they could get care on their own, and with Medicaid paying the cost.

“It’s really easy, four or five years into this expansion from the Affordable Care Act, to forget what it was like for people,” Paul said.

She thinks especially of working parents whose children qualified for coverage under the old criteria but who had no way to pay for their own care. “If you’re a single parent and trying to take care of your kids and be a decent parent, and you can’t even take yourself to the doctor, how can you do it? You’re going to be in big trouble.”

Where Millions Stand To Gain Coverage

More than a thousand miles away, in Boise, Idaho, Penny Beach tells a very similar story ― with one critical twist.

Beach is medical director at the Family Medicine Residency of Idaho, a clinic that serves uninsured patients in and around the city. She doesn’t have to remember what it was like before the Medicaid expansion, because Idaho is one of those 17 states where the Republican officials in charge have refused to take the extra federal money.

Since eligibility hasn’t budged, most of the state’s low-income population still doesn’t qualify.

Jonathan Cohn/HuffPost If Idaho expands Medicaid, Diann Sivels-Sharrer could finally get surgery for an injury that's making it difficult for her to keep working.

Beach, who has been treating underserved populations for roughly 20 years, says that she is sure she’s seen patients suffer because clinics like hers simply can’t provide the kind of specialty services that patients need. Sometimes, she says, patients without insurance are afraid to come in and get tests because they worry so much about how they won’t be able to pay for care.

“I’ve had to admit patients to the hospital, people in their 50s suffering from heart attacks or strokes, because they have never been in to seek care for blood pressure or diabetes, even though maybe they could have found care,” Beach said.

One of Beach’s patients is Diann Sivels-Sharrer, a 57-year-old home health aide. She tends to a mother and daughter, each with mental and physical disabilities, but she also has serious health problems of her own, including a serious tear in her groin muscle that she thinks she got while lifting a wheelchair.

She needs surgery but hasn’t gotten it yet, because she doesn’t have insurance and can’t pay the bills. When I met her a few weeks ago, at the Boise clinic, she needed to stand up and walk around in order to alleviate the pain.

What Voters May Understand ― And What They May Not

Beach and Sivels-Sharrer are hoping for a change in fortunes ― and they may get one. Idaho is one of three deeply conservative states where activists have taken matters into their own hands and gathered signatures for initiatives that would obligate states to accept federal money and expand Medicaid.

In two other states where Republicans have blocked expansion, Florida and Georgia, Democratic gubernatorial candidates Andrew Gillum and Stacey Abrams have pledged to push for expansion if they are elected.

Medicaid has gotten a lot of attention in these states, because of the initiatives and because both Gillum and Abrams have made it centerpieces of their campaigns.

It’s figured into some other campaigns, too, among them Michigan’s gubernatorial race, because the Democratic nominee, former state senator Gretchen Whitmer, helped lead the fight for the state’s expansion while her Republican opponent, Attorney General Bill Schuette, opposed it, although recently he has said the expansion is “not going anywhere.”

But even some of the people who depend on Medicaid seem to realize their coverage depends on the election outcome ― and that they have some power to determine that outcome.

Chelsea is part of Michigan’s 7th U.S. House district and the longtime GOP incumbent, Tim Walberg, is running for re-election. His Democratic challenger, former state legislator Gretchen Driskell, has attacked Walberg for his vote on repeal and pointed out that 49,000 people in his district got coverage because of the expansion.

In the past, Republican critics like Walberg have said that Medicaid is too expensive and it’s true that the program, like any government program, requires spending money that the taxpayers end up shouldering, one way or another. But Medicaid is, if anything, less expensive than private insurance ― and the ACA, on the whole, offsets new government spending with a combination of higher taxes and cuts to other programs.

As it happens, though, Walberg isn’t really making that argument anyway. Like his fellow Republicans around the country, he has tried to avoid the topic, which isn’t surprising given that polls show voters trust Democrats more than Republicans on health care. Driskell is keeping the race close, even though the district has a distinct Republican lean.

When Robertson and I spoke, outside the Chelsea coffee shop, I asked if he knew that the Medicaid expansion’s future was in jeopardy ― and that it might depend, in small part, on who he and other voters in the Michigan 7th send to Congress. He said he hadn’t, though he said he was going to do some research before voting.

“I’m really hoping they don’t take it away,” he said. “That would hurt a lot of people ― really badly.”