COLUMBIA, Mo. — Senator Claire McCaskill isn’t subtle in reminding voters what her campaign is all about. She’s rechristened it the “Your Health Care, Your Vote” tour.
The turnaround could not be more startling. After years of running as far as they could from President Barack Obama’s health care law, Ms. McCaskill and vulnerable Senate Democrats in Florida, West Virginia and other political battlegrounds have increasingly focused their closing argument on a single issue: saving the Affordable Care Act.
Now, with Republicans desperate to reposition themselves and come up with their own health care pitch, and with the elections roiled by gale-force winds on immigration and Justice Brett M. Kavanaugh’s confirmation hearings, the question is whether health care will be enough to save her and Democrats in other key Senate races. Most recently, the mail bombs sent from Florida and the fatal synagogue shooting in Pittsburgh on Saturday have added jagged new pieces with the potential to further disrupt both parties’ strategies.
Ms. McCaskill and her Republican opponent, the Missouri attorney general, Josh Hawley, clashed sharply over health care once again at their final debate on Thursday. She lambasted him for participating in a lawsuit that challenges the constitutionality of the Affordable Care Act and would end its protections for those with pre-existing conditions. He said he supported a program that would protect patients with high medical costs outside the current health care law.
On the same day, President Trump proposed that Medicare pay for certain prescription drugs based on the prices paid in other industrialized countries — just one initiative coming from the White House and Republicans as they try to fight back against perceptions their policies would undo protections for people with pre-existing medical conditions.
And on Friday, Mr. Obama, in speeches in Detroit and Milwaukee, mocked Republican ads on health care, accusing them of trying to rewrite history and their own positions after trying for years to repeal the Affordable Care Act.
It is unknown whether Democrats’ health care message will hold up as Mr. Trump, through almost daily rallies and frequent Twitter blasts, tries to dominate television news and social media in the campaign’s final days. He has said the midterms would be about “Kavanaugh, the caravan, law and order, and common sense.”
But after years of trying and failing to rally voters behind the complicated features of President Obama’s health care law, Democrats have discovered this year the emotional power of one of its benefits, protecting people with pre-existing illnesses.
The subject has lit up polls, monopolized advertising budgets and driven a national strategy for Democrats, who are defending 10 Senate seats in states President Trump won and are relying heavily on health care as a defining issue in key states including Arizona, Florida, West Virginia and Nevada.
“This is the message coming straight from people in the red states,” said Senator Chris Van Hollen of Maryland, chairman of the Democrats’ Senate campaign committee.
Republicans have been put on the defensive, insisting in TV ads featuring their family members that they, too, support affordable care for people with pre-existing conditions.
Their claims come after years of lawsuits and congressional votes by Republicans to gut or weaken the health care law’s protections of expensive chronic illnesses.
In addition to fashioning a message on health care, Mr. Hawley, is relying on a blunt appeal to partisanship. Asked about his campaign’s closing message, Mr. Hawley’s campaign manager, Kyle Plotkin, pointed to the slogan boldly emblazoned on the campaign bus: “Stop Schumer. Fire Claire. Don’t let the liberals take over.”
Callie Glascock, an administrator at the University of Missouri who voted for Mr. Trump, said on Sunday she would cast a ballot for Ms. McCaskill, who is seeking a third term, because of health care. “Everyone wants to say Obamacare was bad. Well, who’s come up with a better plan?” she asked outside a market displaying a hay wagon of pumpkins in Ashland, Mo.
At the same time, her father-in-law, a lifelong Democrat, is leaning toward Mr. Hawley.
“He said, You know what, after watching all that Judge Kavanaugh stuff, he’s about changed his mind on voting Democrat,” said his son, Mike Glascock, who was also at the market. “He just hated all that rhetoric.”
The midterms “are officially about health care,” in the conclusion of the Wesleyan Media Project, whose analysis of television ads in congressional races found that nearly half include discussion of health care.
Two years ago, during the 2016 election, health care was featured in just 10 percent of Democrats’ ads.
A survey by the Kaiser Family Foundation last week found that in two battleground states, Florida and Nevada, nearly seven in 10 voters support protecting people with pre-existing conditions even if it means healthy people would pay more.
Democrats’ reversal of fortune on health care astonishes former Senator Mary Landrieu of Louisiana, who lost her seat in the last midterm cycle, she believes, because of her vote for the Affordable Care Act in 2010.
Before the 2014 campaign season, Ms. Landrieu invited other red-state Democrats up for re-election to her Washington home to brainstorm about reforms they could propose without actually mentioning “Obamacare.” They did not succeed.
Not only Ms. Landrieu but other Democrats were swept away that year in Arkansas, Alaska and North Carolina, handing Republicans the Senate majority.
“The truth is finally winning out,” Ms. Landrieu said of the Affordable Care Act’s increasing popularity in polls. “It didn’t happen fast enough for us.”
National Democrats said the issue bubbled up this year from voters. In fact, the party was taken by surprise last year as Congress was swamped with phone calls and protesters when Republicans tried but failed to repeal the Affordable Care Act in a series of dramatic votes.
Just as the issue was fading a bit from voters’ minds, Republicans in 20 states filed a lawsuit this year to overturn what remains of the law. In June, the Trump administration weighed in. Citing the president’s approval, the Justice Department said it agreed with the need to end the health care law’s guarantees that insurance companies could not deny coverage to people with pre-existing illnesses or charge them more.
“They gave us the political gift of the cycle,” said Brad Woodhouse, executive director of Protect Our Care, an advocacy group on the left.
Since then, Republicans in many close races have scrambled for cover, insisting that they, too, want to protect people with pre-existing conditions.
Two Republican House members running for Senate in battleground states, Representatives Martha McSally of Arizona and Kevin Cramer of North Dakota, argued they voted for Obamacare repeal-and-replace bills in 2017 that would have protected people with pre-existing conditions.
Similarly, Senator Dean Heller of Nevada, the most vulnerable Republican seeking re-election, maintained in a debate last week that he helped write a 2017 bill protecting pre-existing conditions.
Yet the Republican bills watered down or eliminated the protections in existing law. They would have allowed states to receive waivers to let insurers charge higher premiums for unhealthy people.
Nowhere is the issue more important than in the close race in Missouri.
Ms. McCaskill, 65, recounts on the campaign trail how, when she was a young lawyer, her parents were forced to move in with her after her father lost his job and his insurance because of a brain tumor. “I remember hearing my mother in the next room being very upset because she was so frightened,” she said at a rally last Friday.
Mr. Hawley, as Missouri’s attorney general, is a plaintiff in the multistate lawsuit that would terminate the Affordable Care Act altogether.
Facing criticism on the issue, he recorded an ad in which he tells of learning that his 5-year-old son has a chronic disease and says he will force insurance companies to cover pre-existing conditions.
In a newspaper column, Mr. Hawley proposed that the federal government pay expenses above $10,000 for people with pre-existing conditions. His plan included no details on how the government would raise the money to cover these costs.
Ms. McCaskill blasted it as “a press release plan” in a debate last week. “You can’t go to court and get rid of important protections when there is no backup, when people will be in a free fall,” she said.
In an interview on Saturday, after he had walked in the University of Missouri homecoming parade, Mr. Hawley, 38, said that his plan would cost only “a fraction” of the Affordable Care Act. He attacked Ms. McCaskill for being unwilling to consider solutions that are not part of Obamacare. The 2010 law offset expenses for people with existing illnesses by requiring healthy people to buy insurance — a mandate since eliminated by Republicans.
For all the Democrats’ focus, it is uncertain how the issue will influence voters.
John Kosach, a 32-year-old public relations researcher in a St. Louis suburb, said he supported Ms. McCaskill. “Claire’s message of saying Hawley is going to repeal the law but there isn’t a plan in place, that’s resonated with me,” he said.
His wife, Sam Kosach, 31, who also works in public relations, said Mr. Hawley’s use of his family in the ad about his support for pre-existing conditions “just felt icky.”
Another voter, Karen French, a 59-year-old retired nurse, is part of the large bloc of conservatives who crossed party lines in the past to vote for Ms. McCaskill, one of only two Missouri Democrats in statewide office.
This year, however, she will not do so.
“I’m kind of ashamed of my country and the mess we made of Judge Kavanaugh’s life,” she said. “I probably would have voted for Claire until that happened.”
Ms. French, who lives in rural Fulton, Mo., has a 28-year-old daughter who has severe problems with her heart and lungs. Asked if she was worried that Mr. Hawley’s lawsuit would threaten protections for people like her daughter, Ms. French broke in before a reporter could finish the question.
“It doesn’t matter to me,” she said. “More important is the situation that happened with Judge Kavanaugh.”