(Reuters) - Democratic candidates for the U.S. Congress are closing out the campaign season with an ominous warning: telling voters millions of Americans could lose their health insurance or be forced to pay significantly more if Republicans win.

A Reuters/Ipsos poll released on Friday shows why they are hammering the message: 58 percent of likely voters want to keep former President Barack Obama’s signature legislative achievement, the Affordable Care Act.

Among other things, the law protected insurance coverage for people with pre-existing health conditions. The poll, conducted Oct. 12-17, also showed that eight in 10 likely voters from each major party want to protect coverage for people with existing conditions, such as heart disease, diabetes or cancer.

With the Nov. 6 elections looming, Democrats are reminding voters of Republicans’ often-repeated promises to repeal the 2010 law. Many Republican candidates are softening their tone or removing website references decrying what they long derided as “Obamacare,” according to candidates, analysts and healthcare experts in both parties.

As Democrats seek to take control of Congress, they see Republicans as having a particularly weak spot on healthcare. Sixty-seven of the 73 most vulnerable Republican incumbents in the House of Representatives voted at least once to eliminate the ACA and its protections for pre-existing conditions, according to the Center for American Progress Action Fund.

Some of those votes date back to the Obama administration, though his successor, Republican President Donald Trump, also campaigned on a promise to undo the law. A repeal attempt after Trump took office last year failed.

Opinion polls show Democrats as having a chance to achieve the net gain of 23 seats they would need to take a majority in the House, but facing a longer shot at picking up the two seats they need to take control of the Senate.

Democratic activists said the repeated Republican attempts to repeal the ACA provide a powerful tool to motivate voters.

“Healthcare has an ability to move people into action,” said Ben Wikler, Washington director of liberal activist group MoveOn. “It is turning people out in town hall meetings ... getting people to make hundreds of thousands of phone calls and getting voters to the polls.”

‘ANXIOUS’ ABOUT HEALTHCARE

FILE PHOTO: A woman holds a sign during a press conference held by U.S. Sen. Bob Casey, D-Pa., to speak out against the latest Republican effort to repeal Obamacare on Capitol Hill in Washington, U.S., September 25, 2017. REUTERS/Kevin Lamarque/File Photo

One sign of Democratic focus: 54.5 percent of Democrats’ federal election ads from Sept. 18 to Oct. 15 mentioned healthcare, far more than the 8.7 percent that did so at the same time in 2010, according to the Wesleyan Media Project.

Some 33.9 percent of Republican federal election ads mentioned healthcare during this period and 31.5 percent in 2010. Republicans took control of the House in the 2010 midterm elections, boosted in part by opposition to the ACA, which had become law earlier that year.

While the aim of the ACA was to expand healthcare insurance to reach millions of Americans who did not have any coverage, Republicans campaigned for years against it as government overreach, especially its requirement that people buy health insurance or pay a financial penalty.

U.S. Senator Claire McCaskill has made healthcare the focus of her campaign in Missouri against Republican challenger Josh Hawley. The state’s attorney general, Hawley has faced criticism from individuals and healthcare groups for saying he supports covering pre-existing conditions even after suing to end the ACA.

“Everyone is feeling anxious and worried about the future of healthcare,” McCaskill said in a telephone interview. “It’s beginning to dawn on people that the Republicans didn’t have a replacement (for the ACA), and that they have no ideas on how they could do it better.”

Hawley ran for state attorney general by emphasizing his role in a lawsuit against the ACA that went to the U.S. Supreme Court, and also worked on a team that successfully challenged the ACA’s requirement to provide contraceptives coverage.

Hawley declined interview requests.

‘IT HAD BECOME REAL’

Despite Republican opposition, eight years after its passage many Americans have seen some benefits from the law.

“By the time Republicans last year tried to repeal the law, it had become real, people had benefited,” said Brad Woodhouse, executive director of Protect Our Care. He said at least 20 Republican incumbents have “scrubbed” their websites to appear more supportive of the law.

In Kentucky, Representative Andy Barr has called his vote to repeal the ACA “a great day for freedom in America” but now plays up his support of programs to prevent and treat opioid addiction. In Maine, Representative Bruce Poliquin dropped a promise to “end Obamacare” and now talks about protecting hospitals.

Ted Cruz, a U.S. senator from Texas, said during a debate this month against Democratic challenger Beto O’Rourke that he would protect pre-existing illnesses, despite having once forced a shutdown of the federal government over ACA repeal efforts.

In a hotly contested upstate New York congressional race, Democratic challenger Antonio Delgado has hammered his opponent, first-term Republican John Faso, over his vote to repeal the ACA.

“John Faso, despite voting to take away protections, is running TV ads saying the exact opposite,” he said during a recent town hall meeting. ”How can you look someone in the face and say, ‘No, I didn’t do that.’ After a while, you’re just lying to our faces blatantly. This is too real to lie about.”

Faso defended his vote in an interview, saying New York state law already ensures patients with pre-existing conditions are protected, regardless of federal legislation.

DIM VIEW OF HEALTHCARE

Despite support for specific elements of the law, 52 percent of likely voters told Reuters/Ipsos they view the U.S. healthcare system as “poor” or “terrible.”

Some 27 percent blame Democrats and Obama for the system, while 20 percent view Republicans and Trump as responsible.

The Reuters/Ipsos poll was conducted online in English throughout the United States. It gathered responses from 1,792 adults including 925 likely voters. The poll has a credibility interval, a measure of accuracy, of 3 percentage points for the entire sample and 4 percentage points for likely voters.

“I don’t think it is a clear win for Democrats,” said Matt Mackowiak, who advises Republican candidates, speaking of healthcare as an election issue. “It’s tough to pin the entire blame on Republicans when they’ve been in control for a year and a half.”

Still, Democrats are betting the threat of losing healthcare coverage will motivate young and minority voters who often do not vote in non-presidential elections.

They are focusing on people like Shane Kehoe, 26, of Livingston, Montana, who plans to vote next month for the first time because he wants Democratic U.S. Senator Jon Tester to fend off a challenge to his seat.

“I want to make sure the insurance stays in place,” said Kehoe, a restaurant employee who has had foot surgery. “What we’re voting on is covering pre-existing conditions.”

Full Reuters election coverage: here