WASHINGTON — Democrats’ plan to take back the House of Representatives in November is all about health care. The unpopularity of Republican plans to replace Obamacare, combined with ever-rising health care costs, has led to a deluge of Democratic ads about protecting patients with pre-existing conditions and expanding Medicaid.

That all-health-care, all-the-time strategy might find its stiffest test in Michigan’s 6th District, where a Democratic doctor has a chance to take down the man who saved the GOP’s Obamacare repeal efforts in spring 2017.

Rep. Fred Upton (R) is running for his 16th term representing a district centered around Kalmazoo and covering most of the southwestern portion of Michigan’s lower peninsula. Upton, a relative moderate who an ally described as possessing a “nerdy Midwestern charisma,” initially opposed the Republican plan to repeal and replace Obamacare. But he later revitalized the proposal, saving it from defeat by crafting a compromise he said would better protect people with pre-existing medical conditions from losing health insurance. (Democrats, and experts, disagree.)

The Democrat looking to take him down is Matt Longjohn, a doctor and the former national health director for the YMCA who the Obama administration named one of the top health care innovators in the country for his work on diabetes prevention.

Not surprisingly, Longjohn is focused on health care — and Upton’s role in passing Obamacare repeal through the House. (It failed in the Senate, thanks to a late-night “no” vote from the late John McCain.)

“He didn’t just vote to stop protecting pre-existing conditions, he put his name on it,” Longjohn said, referring to the Upton Amendment. “He’s sided with corporate donors and big business. He’s never put solutions forward.”

Upton has been in the House since 1987, and the general public might know him best as the uncle of supermodel Kate Upton. In Congress, however, he’s considered a political survivor and a bipartisan dealmaker, known as the former chair of the House Energy and Commerce Committee. His district isn’t overwhelmingly Republican — GOP Presidential nominee Mitt Romney narrowly won it in 2012 — but Upton has never earned less than 55 percent of the vote.

But there are signs this race is more competitive. While the major Democratic and Republican outside groups have stayed out so far, a super PAC controlled by allies of House Speaker Paul Ryan has reserved $400,000 worth of television airtime for the final two weeks of the election. And Longjohn released an internal poll showing him trailing by just five percentage points last month.

Smaller Democratic groups are up on the air attacking Upton over his health care vote, and trying to persuade the district’s residents their longtime congressman can no longer be trusted.

“Congressman Upton — who I used to vote for — led the charge to repeal health care and protections for pre-existing conditions,” a woman named Kim from St. Joseph says in an ad from Change Now. “That could be disastrous for families like mine.”

But those ads are being canceled out by a spot from the American Hospital Association, which is airing ads boosting Upton even though they officially opposed his amendment and the GOP’s entire Obamacare repeal effort.

The ads, which tout Upton as “one of America’s health care leaders” and emphasize his work on mental health issues and the opioid epidemic, are backed by a $300,000 television buy, according to a media-tracking source. The AHA’s involvement has caused grumbling among Democrats.

“Dropping big money to tout the health care record of the GOP Congressman who got repeal to pass is a sad reminder that the health care industry cares more about their profits than their patients,” said one Democratic operative who’s worked extensively on health care this cycle and requested anonymity to avoid aggravating the powerful lobby. “Running ads to reinvent Fred Upton as a good leader on health care would be like running ads that reinvent Donald Trump as a spokesman for Jenny Craig.”

Longjohn offered a similar explanation: “I will say we have to recognize the American health care system has nonprofit and for-profit institutions,” he said. “The tax bill was very friendly to large corporations.”

Marie Johnson, a spokesperson for the American Hospital Association, offered a one-line explanation in an email: “Rep. Upton has been a leader in improving access to mental health services and working across party lines to address the opioid crisis and has worked to reduce soaring drug prices.”

Upton’s allies, meanwhile, are taking aim at Longjohn’s credentials, noting that he isn’t actually licensed to practice medicine in Michigan, even though he graduated from medical school.

“If Longjohn is willing to misrepresent himself about this, where does he draw the line?” Sarah Anderson, the Michigan GOP’s deputy chief of staff, told the Detroit Free Press. “Southwestern Michigan deserves to be represented by a leader who tells the truth. Not someone who is willing to say anything in order to win an election.”

Upton is also airing spots attacking Longjohn as a puppet of House Speaker Nancy Pelosi, saying he would “rubberstamp Pelosi’s liberal agenda.”

Longjohn’s campaign insists the attacks are a sign Upton is worried about the race, noting Upton hasn’t gone negative against opponents in the past.

The Upton campaign, meanwhile, says there’s nothing to see here.

“Fred has a long bipartisan history when it comes to health care issues,” campaign manager Nate Henschel said, pointing to Upton’s work on extending the Children’s Health Insurance Program and on legislation rolling back regulations on the pharmaceutical industry. “We feel really good about where our campaign is.”