Health Care Powered Democratic Wins in 2018. The Party Hopes for a Repeat.

At the Democratic National Convention, viewers heard from an Arizona man whose young son was…

Health Care Powered Democratic Wins in 2018. The Party Hopes for a Repeat.

At the Democratic National Convention, viewers heard from an Arizona man whose young son was born with a congenital heart defect, a Wisconsin woman with an autoimmune disease and cancer survivors from several states. Their stories highlighted the importance of health care — and the protections provided by the Affordable Care Act.

When Republicans held their convention last week, they had little to say about their own vision for America’s health care system. Obamacare, for years a punching bag for the party, went almost entirely unmentioned. When the phrase “health care” was spoken, it was often in the service of attacking Democrats over health care for undocumented immigrants.

Those dueling approaches to discussing health policy offered a preview of what to expect as the two parties, and their presidential nominees, make their closing arguments on one of the most critical issues to many voters — one whose importance has been underscored by the coronavirus pandemic, which has killed at least 184,000 people in the United States.

Democrats are once again trying to capitalize on an issue that was key to their success in the 2018 midterm elections. And Republicans are once again vulnerable: Three years after failing to repeal and replace the Affordable Care Act, the party still has not coalesced around a plan for the future of America’s health care system.

“No one could quite figure out what ‘replace’ was,” said Adam Brandon, the president of FreedomWorks, a conservative advocacy group, as he recalled the party’s struggle to repeal the law known as Obamacare after President Trump’s election. “That’s where the problem was, and we never recovered from it. And we still haven’t recovered from it today.”

Mr. Brandon cited the successful health care message employed by Democrats in 2018, with its emphasis on protecting people with pre-existing medical conditions, and likened it to a football team that calls a running play that proves successful — and then keeps calling the same play. “If I’m the Democrats,” he said, “I just keep handing the ball off on pre-existing conditions until Republicans prove they can stop that.”

It’s a playbook that down-ballot Democrats and their allies are using in campaign ads.

“Tell Thom Tillis: Stop cutting health care,” the narrator says in several recent ads attacking Mr. Tillis, a Republican senator up for re-election in North Carolina. And an ad from Amy McGrath, the Democratic challenger to Senator Mitch McConnell of Kentucky, says of her opponent: “Even during a pandemic, with people out of work, he’s trying to take away health care.”

With two months until Election Day, health care is looming as a major weak spot for Republicans, including incumbent senators in close races that could determine which party wins the majority. In a Fox News poll in August, 53 percent of voters disapproved of the way Mr. Trump was handling health care, while Joseph R. Biden Jr. led Mr. Trump by a 15-point margin when voters were asked whom they trusted to do a better job on health care.

The Trump administration is also asking the Supreme Court to overturn the Affordable Care Act, a course of action that offers Democrats a political piñata to swing at in the weeks leading up to Election Day. And that is in addition to the matter of how Mr. Trump has handled the pandemic, a front-and-center issue that is shaping up to be a major liability for Republicans.

“This is my promise to you: When I’m president, I will take care of your health care coverage and your family the same way I would my own,” Mr. Biden said during a segment on health care. In his speech accepting the Democratic nomination, he warned that if Mr. Trump is re-elected, “the assault on the Affordable Care Act will continue until it’s destroyed.”

Mr. Biden’s victory in the Democratic primary has also left his party’s candidates less susceptible to being attacked on health care than they might have been if a more progressive candidate had prevailed. Mr. Biden, who was vice president when the Affordable Care Act was passed, does not support “Medicare for all,” a government-run health insurance system under which private insurance would be eliminated; instead, he wants to build on the health law by offering a government plan known as a public option. Had a supporter of Medicare for all, like Senator Bernie Sanders of Vermont, been atop the Democratic ticket, Republicans would have been able to use the issue of private insurance as a cudgel.

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The Trump campaign is nevertheless mounting an attack in that vein, arguing that a public option would open the door to a larger government role in health care in the future. Mr. Biden’s proposal, the campaign said in August, “will ultimately kill families’ private health plans and pave the way for Bernie Sanders’s socialist single-payer system.”

“Who has private health insurance here?” Mr. Trump asked the crowd at a rally in New Hampshire last week. “And you love it, right? You love it. It’s luxury, it’s good, it’s beautiful and you have the greatest — you’re going to lose it. Hate to tell you. Under his plan, you’re going to lose your private health care.”

Lanhee J. Chen, a fellow at the Hoover Institution who was policy director for Mitt Romney’s 2012 presidential campaign, said the critique of Mr. Biden on health care reinforced the Republican argument that Mr. Biden “is a Trojan horse for bad progressive outcomes.”

“The fact that Biden is for a public option is enough to usher in the possibility that he could also be for Medicare for all at some point, or that Medicare for all would be the likely outcome,” he said. “If Republicans repeat enough, ‘Trojan horse,’ ‘single payer,’ that’s going to leave a mark.”

But even if that critique sticks with some voters, the Republican Party will still have to overcome its recent history of missteps on health care.

In 2016, Mr. Trump stood onstage at his party’s convention and offered an unequivocal pledge: “We will repeal and replace disastrous Obamacare.” But that goal proved elusive. In 2017, after considerable difficulty, Republicans in the House passed a bill to repeal and replace the health law, a step that Mr. Trump celebrated in the Rose Garden, but Republicans in the Senate could not agree on their own measure. As part of the tax overhaul passed later that year, Mr. Trump and Republicans did manage to scrap one piece of the Affordable Care Act, eliminating the penalty for people who choose not to buy health insurance.

Despite the failure to repeal the law, the Trump administration has taken a number of steps to undermine it, and the administration is now asking the Supreme Court to overturn it. Oral arguments are scheduled for one week after Election Day. The administration’s legal position has handed Democrats a simple and powerful talking point: that Mr. Trump is threatening the health care of millions of Americans in the midst of a pandemic.

“Instead of crushing the virus, he’s trying to crush the Affordable Care Act,” Speaker Nancy Pelosi of California said last week.

The lack of a crystal clear message on health care was not a surprise, because Mr. Trump has been anything but clear on the subject.

Mr. Trump and his campaign have tried to put a focus on the cost of prescription drugs, with a series of executive orders and a television ad that proclaims Mr. Trump is “standing up to the drug companies.” (One of those orders still has not been released publicly.)

But more than three years into his presidency, Mr. Trump’s plans for the future of the overall health care system remain a question mark. In July, he said, “We’re signing a health care plan within two weeks, a full and complete health care plan.” Two weeks later, no health care plan had materialized. Mr. Trump then offered a new time frame, promising “a tremendous health care plan” before the end of August and adding that it was “just about completed.”

The end of August came and went without any plan. Asked for an update, a White House spokeswoman, Sarah Matthews, cited Mr. Trump’s executive orders on prescription drugs and promised “more action to come in the coming weeks,” without providing any specifics.

Mr. Trump has also teased an executive order protecting people with pre-existing conditions, a curious undertaking given that the Affordable Care Act already protects people with pre-existing conditions.

And when he addressed Republican delegates gathered in Charlotte, N.C., last week, he declared that “we knocked out Obamacare.”

There was only one problem: Obamacare still exists.