In an otherwise confident debate performance on Tuesday, the Republican vice-presidential nominee, J. D. Vance, conspicuously dodged questions from the CBS moderators about his views on health care. For weeks, Vance has made clear his desire to dismantle one of the central pillars of the Affordable Care Act: the law’s provisions that require the sharing of risk between the healthy and the sick. On Tuesday, though, Vance refused to elaborate on his plans to reconfigure the ACA, instead pressing the implausible argument that Donald Trump—who sought to repeal the law, and presided over a decline in enrollment during his four years in office—should be viewed as the program’s savior.

Vance’s evasive response to the questions about health care, on a night when he took the offensive on most other subjects, exposed how fraught most Republicans still consider the issue, seven years after Trump’s attempt to repeal the ACA died in the Senate. But Vance’s equivocations should not obscure the magnitude of the changes in the program that he has signaled could be coming in a second Trump presidency, particularly in how the law treats people with significant health problems.

The ACA provisions that mandate risk-sharing between the healthy and sick underpin what polls show has become its most popular feature: the requirement that insurance companies offer coverage, at comparable prices, to people with preexisting conditions. In numerous appearances, Vance has indicated that he wants to change the law to restore to insurance companies the ability to segregate healthy people from those with greater health needs. This was a point that Tim Walz, the Democratic vice-presidential nominee, accurately stressed during the debate.

The political paradox of Vance’s policy is that the trade-off he envisions would primarily benefit younger and healthier people, at a time when most young people vote Democratic. Conversely, the biggest losers would be older adults in their last working years before they become eligible for Medicare. That would hit older working-class adults, who typically have the biggest health needs, especially hard. Those older working people are a predominantly white age cohort that reliably favors the Republican Party; in 2020, Trump won about three-fifths of white voters ages 45 to 64, exit polls found. The threat that the GOP’s ACA alternatives present to these core Republican voting groups represents what I called in 2017 “the Trumpcare conundrum.”

“Going back to the pre-ACA days of segregated risk pools would lower premiums for young and healthy people, but result in increased cost and potentially no coverage at all for those with preexisting conditions,” Larry Levitt, the executive vice president for health policy at the nonpartisan KFF (formerly known as the Kaiser Family Foundation), told me.

Vice President Kamala Harris’s campaign hopes to exploit that tension by launching a major advertising campaign across swing states this week to raise an alarm about the plans from Trump and Republicans to erode the ACA’s coverage. Support for the ACA—in particular, its provisions protecting people with preexisting conditions—may be one of Harris’s best assets to hold support from older and blue-collar white women, who may otherwise be drawn to Trump’s argument that only he can keep them safe from the threats of crime and undocumented immigration.

[Helen Lewis: Did Donald Trump notice J. D. Vance’s strangest answer?]

The efforts of Republicans like Vance to roll back the ACA this long after President Barack Obama signed it into law, in 2010, are without historical precedent: No other major social-insurance program has ever faced such a lengthy campaign to undo it. After Franklin D. Roosevelt signed Social Security into law in 1935, Alf Landon, the GOP presidential nominee in 1936, ran on repealing it. But when he won only two states, no other Republican presidential candidate ever again ran on repeal. And no GOP presidential candidate ever ran on repealing Medicare, the giant health-care program for the elderly, after President Lyndon B. Johnson signed it into law in 1966.

By contrast, this is the fourth consecutive election in which the GOP ticket has proposed repealing or restructuring the ACA—despite polling that shows the act’s broad popularity. During Trump’s first year in office, House Republicans passed a bill to rescind the law without support from a single Democrat. The repeal drive failed in the Senate, when three Republican senators opposed it; the final gasp came when the late Senator John McCain voted no, giving a dramatic thumbs-down on the Senate floor.

Most health-care analysts say that, compared with 2017, the ACA is working much better today. At that point, the ACA exchanges had begun selling insurance only three years earlier, following a disastrously glitchy rollout of the federal website that consumers could use to purchase coverage. When congressional Republicans voted on their repeal plans, about 12 million people were receiving coverage through the ACA, and the stability of the system was uncertain because insurers feared that too many of those buying insurance on the exchanges were sicker people with more expensive health needs.

“In 2017, not only did we have rising premiums because insurance companies were worried the market was getting smaller and sicker, but we also had insurance companies exiting markets and raising the risk that parts of the country would have nobody to provide coverage,” Sabrina Corlette, a professor at Georgetown University’s Center on Health Insurance Reforms, told me.

Today, however, “we are in a very, very different place,” she said. “I would argue that the ACA marketplaces are thriving and in a very stable” condition. The number of people purchasing insurance through the ACA exchanges has soared past 21 million, according to the latest federal figures. Premiums for plans sold on the ACA exchanges, Corlette said, are rising, but generally not faster than the increase faced by employer-provided insurance plans. And enough insurers are participating in the markets that more than 95 percent of consumers have access to plans from three or more firms, according to federal figures.

Despite Vance’s portrayal of Trump as the program’s savior, the number of people receiving coverage through the ACA exchanges actually declined during Trump’s term, to 11.4 million, after he shortened the enrollment period and cut the advertising promoting it. The big leap forward in ACA participation came when the Democratic-controlled Congress in 2021 passed a major increase in the subsidies available to people for purchasing insurance on the exchanges. That made a mid-range (“silver”) insurance plan available for people earning up to 150 percent of the poverty level at no cost, and ensured that people earning even four times that level would not have to pay more than 8.5 percent of their income on premiums.

“The biggest criticism of the ACA from the start, which in many ways was legitimate, was that the coverage was not truly affordable,” Levitt said. “The enhanced premium subsidies have made the coverage much more affordable to people, which has led to the record enrollment.”

Neera Tanden, the chief domestic-policy adviser for President Joe Biden, told me that the steady growth in the number of people buying insurance through the ACA exchanges was the best indication that the program is functioning as intended. “A way to determine whether a program works is whether people are using it,” Tanden said. “No one is mandated to be in the exchanges, and they have grown 75 percent in the past four years. This is a program where people are voting with their feet.”

Conservative critics of the law nonetheless see continuing problems with the system. Michael Cannon, the director of health-policy studies at the libertarian Cato Institute, points out that many insurers participating in the ACA exchanges limit their patients to very narrow networks of doctors and hospitals, a trend acknowledged even by supporters of the law. And Cannon argues that the continued rise in premiums for plans sold on the ACA show that it has failed in its initial ambition to “bend the curve” of health-care spending, as Obama often said at the time.

The ACA “has covered marginally more people but at an incredible expense,” Cannon told me. “Don’t tell me it’s a success when it is exacerbating what everyone acknowledges to be the main problem with the U.S. health sector”—the growth in total national health-care spending.

Other analysts see a more positive story in the ACA’s effect on coverage and costs. The insurance exchanges established by the ACA were one of the law’s two principal means of expanding coverage for the uninsured. The second prong was its provision providing states with generous grants to extend Medicaid eligibility to more working, low-income adults. Although 10 Republican-controlled states have still refused to extend eligibility, nearly 24 million people now receive health coverage through the ACA’s Medicaid expansion.

Combined with the roughly 21 million receiving coverage through the exchanges, that has reduced the share of Americans without insurance to about 8 percent of the population, the lowest ever recorded and roughly half the level it was before the ACA was passed.

Despite that huge increase in the number of people with insurance, health-care spending now is almost exactly equal to its level in 2009 when measured as a share of the total economy, at slightly more than 17 percent, according to KFF figures. (Economists usually consider that metric more revealing than the absolute increase in spending.) That share is still higher than the equivalent figure for other industrialized countries, but Levitt argues that it counts as an overlooked success that “we added tens of millions of people to the health-insurance rolls and did not measurably increase health-care spending as a result.”

[David Frum: The Vance warning]

The ACA’s record of success underscores the extent to which the continuing Republican opposition to the law is based on ideological, rather than operational, considerations. The GOP objections are clustered around two poles.

One is the increase in federal spending on health care that the ACA has driven, through both the generous premium subsidies and the costs of expanding Medicaid eligibility. The repeal bill that the House passed in 2017 cut federal health-care spending on both fronts by a total of about $1 trillion over a decade. This spring, the conservative House Republican Study Committee released a budget that proposed to cut that spending over the same period by $4.5 trillion; it also advocated converting Medicaid from an entitlement program into a block grant. Every serious analysis conducted of such proposals has concluded that they would dramatically reduce the number of Americans with health insurance.

Even if Republicans win unified control of Congress and the White House in November, they may not be able to muster the votes for such a sweeping retrenchment of federal health-care spending. (Among other things, hospitals in reliably red rural areas heavily depend on Medicaid.) At a minimum, however, Trump and congressional Republicans would be highly unlikely to extend the enhanced ACA subsidies that expire at the end of 2025, a move that could substantially reduce enrollment on the exchanges.

The other main Republican objection is the issue that Vance has highlighted: the many elements of the ACA that require risk-sharing between the healthy and the sick. The ACA advanced that goal with an array of interlocking features, including its core protection for people with preexisting conditions.

In varying ways, the GOP alternatives in 2017 unraveled all of the law’s provisions that encouraged risk-sharing—by, for instance, allowing states to override them. That triggered the principal public backlash against the repeal effort, as Americans voiced their opposition to rescinding the ACA’s protections for people with preexisting conditions. But Vance has made very clear that a second Trump administration would resume the effort to resurrect a pre-ACA world, in which insurers sorted the healthy from the sick.

“A young American doesn’t have the same health-care needs as a 65-year-old American,” Vance argued recently on Meet the Press. “A 65-year-old American in good health has much different health-care needs than a 65-year-old American with a chronic condition.” Although “we want to make sure everybody is covered,” Vance claimed, “the best way to do that is to actually promote some more choice in our health-care system and not have a one-size-fits-all approach.”

Supporters of this vision, such as Cato’s Cannon, argue that it would allow younger and healthier people to buy less comprehensive plans than the ACA now requires, at much lower cost. As those more affordable options become available, Cannon says, cutting Medicaid spending to the degree Republicans envision would be more feasible, because people currently covered under that program could instead purchase these skimpier but less expensive private-insurance policies. Government-subsidized high-risk pools, the argument goes, could provide affordable coverage for the people with greater health needs whom insurers would weed out from their new, slimmed-down plans.

“If you want to make health care universal, you need to give insurers and consumers the freedom to agree on the prices and terms of health-insurance contracts themselves,” Cannon told me. “You need to let market competition drive the premiums down for healthy people as low as possible so they can afford coverage.”

Supporters of the ACA generally agree with the first point: that a deregulated system would allow insurers to create less expensive plans for young, healthy people. But they believe that all the arguments that follow are mistaken. Initial premiums might be lower, but in a deregulated system, even young and healthy families might find comprehensive policies, including such coverage as maternity benefits, unaffordable or unavailable, Georgetown’s Corlette told me. And when, before the ACA, states sought to establish high-risk pools for people with greater health needs, those efforts almost uniformly failed to provide affordable or adequate coverage, she pointed out.

Even if a reelected Trump lacks the votes in Congress to repeal the ACA’s risk-sharing requirements, he could weaken them through executive-branch action. In his first term, Trump increased the availability of short-term insurance plans that were free from the ACA’s risk-sharing requirements and its protections for people with preexisting conditions. Biden has shut down such plans, but if Trump won a second term and reauthorized them, while ending the enhanced subsidies, that could encourage many healthy people to leave the exchanges for those lower-cost options. Such actions would further the goal of Vance and other ACA critics of separating the healthy and sick into separate insurance pools.

Vance’s most revealing comment about this alternative vision may have come during a recent campaign stop in North Carolina, when he said that his proposed changes to the ACA would “allow people with similar health situations to be in the same risk pools.” But—as many health-policy experts noted to me, and Walz himself observed last night—that notion rejects the central purpose of any kind of insurance, which is to spread risk among as many people as possible—which, in fact, may be the point for Vance and other conservative critics of the ACA.

“The far right,” Tanden told me, “has always believed people should pay their own way, and they don’t like the fact that Social Security, Medicare, the ACA are giant social-insurance programs, where you have a giant pooling of risk, which means every individual person pays a little bit so they don’t become the person who is bankrupted by being sick or old.”

To date in the presidential race, health care has been eclipsed by two other major issues, each foregrounded by one of the nominees: immigration for Trump, and abortion for Harris. Under the glare of the CBS studio lights on Tuesday night, Vance was tactical in saying very little about his real health-care ideas. But the arguments he has advanced aggressively against crucial provisions of the Affordable Care Act have made clear that its future is still on the ballot in 2024.