In speeches, in tweets, in media interviews, President Trump keeps promising that he will preserve protections for Americans with pre-existing health conditions. It’s a crowd-pleaser of a policy, but one entirely at odds with his administration’s legislative, regulatory and legal record to date.

In the final weeks of the election season, expect to see the words “pre-existing conditions” again and again. Mr. Trump makes the promise so consistently that it is likely to appear in television ads, the presidential debates and possibly in an oft-teased, ever forthcoming executive order on the subject. Vice President Pence said Tuesday that the president would “take action” in the days ahead.

But rather than enshrine the ability of Americans with health problems to buy insurance, the Trump administration has, at every turn, pursued policies that have tended to do the opposite.

Some of the efforts to weaken protections have been successful — like an expansion of cheap, lightly regulated health plans that insurers are not required to offer when customers are sick. Others, like multiple attempts to “repeal and replace Obamacare” in 2017, failed to attract enough Republican votes in Congress to pass. The Justice Department’s quest to overturn the Affordable Care Act, while no replacement is being offered, is still underway, with oral arguments scheduled at the Supreme Court in November.

“We will always and very strongly protect patients with pre-existing conditions,” Mr. Trump said in his speech at the Republican National Convention. “We will protect your pre-existing conditions,” he said at a recent campaign rally in Las Vegas. In January, he went as far as to say he “saved pre-existing conditions.”

Yet despite a record to the contrary, these repeated statements seem to be having an impact. A recent survey from the Kaiser Family Foundation found that 84 percent of Republicans believe President Trump has a better approach for “maintaining protections for people with pre-existing conditions.” (Over all, 38 percent of American adults said they thought Mr. Trump had the better approach.)

Before Obamacare, Americans with a history of both serious and trivial diseases had trouble buying health insurance. Health plans could omit coverage for addiction, could charge customers higher prices because of a history of acne, or could simply decline to sell insurance altogether to someone who’d had a cancer diagnosis. All of those practices were eliminated as part of Obamacare, which requires insurance companies to offer the same, comprehensive health plans to everyone in a geographic area, varying the prices based only on the customer’s age.

This provision has long been one of the Affordable Care Act’s most popular features. Even when a majority of Americans disliked the law over all, most supported this part of it. Over time, as Obamacare has become more popular and more embattled, pre-existing-condition protections have become so popular that any politician who declines to support them is likely to pay a political price. In 2018, Democrats retook control of the House of Representatives, after campaigning heavily on pre-existing conditions as an issue.

“I think it’s gotten to the point where every politician has to say they’re for protecting people with pre-existing conditions,” said Larry Levitt, the executive vice president for health policy at the Kaiser Family Foundation. “And then the question is: How far are they wiling to go in providing those protections?”

That popularity probably explains why President Trump keeps repeating the words “pre-existing conditions.” But saying that he will support these rules doesn’t make it true. His policies to date have slightly weakened the Obamacare framework, providing some escape hatches where healthier customers can buy unregulated, cheaper insurance. Because Obamacare is also on the books, people with pre-existing conditions can buy plans, too. But President Trump has repeatedly pressed to eliminate the Affordable Care Act. The Justice Department filed a brief asking for the wholesale erasure of the law as recently as June.

“If there’s any merit in the president’s record on pre-existing conditions, it is purely by accident,” said Michael Cannon, the director of health care policy studies at the libertarian Cato Institution. Mr. Cannon, who favors a less regulated health insurance market, is no fan of Obamacare, but says that Mr. Trump has little to support his claims.

Defenders of the president’s health policies point to the ways he has worked to lower the cost of care and expand consumer choice. The skimpier plans his policy expanded did lower prices for Americans who are fortunate enough to qualify and want coverage with limited benefits, and they did expand the ability of people who bought them to keep them longer. His expansion of health reimbursement accounts may pave the way for people who currently get work-based coverage to select their own plans. His new rules expanding the transparency of hospital prices may come to lower those prices over time. Recent executive orders may lead the way to new policies regulating prescription drug prices.

But none of the president’s health policies have offered new consumer protections for the sick who seek health insurance.

Recent reports that the president will release an executive order to protect pre-existing conditions are puzzling, since such protections are already the law. If Obamacare were overturned, such an order would be toothless. Major new regulations of the health insurance industry would require legislation, which is why the Trump administration pursued Obamacare replacement in Congress in the first place.

The structure of the Affordable Care Act, of course, is not the only way to protect people with pre-existing conditions. Obamacare sets up one system with highly regulated private insurance markets and a system of federal tax credits to help low- and middle-income Americans buy insurance.

But other systems could also offer some level of protection for the sick. A single-payer system, like the “Medicare for all” plans championed by Senator Bernie Sanders and other progressives in Congress, would provide standardized government health insurance to Americans of all health histories. And there are other possible approaches that may appeal more to conservatives, such as well-funded high-risk pools, which would offer special coverage to the sick while keeping it affordable.

President Trump may have some other policy idea in mind to protect Americans with pre-existing health conditions. But there is no evidence from his record. Nearing four years into his presidential term, he has repeatedly promised to release a comprehensive health plan, then declined to do so. He and his staff are often asked about how he will fulfill this promise, and have offered no specific reply. If protecting pre-existing conditions is a priority of the president, it’s not clear why his strategy is still a secret.