But Tanner agrees that under the GOP alternatives “there are going to be winners and losers … and the losers are most likely to be older, sicker, blue-collar workers, which is a Trump constituency. The winners are going to be educated, white-collar, wealthier, and younger people who were not the Trump constituency.”

This inversion is rooted in the Republican determination to unravel the sharing of risk that Obamacare aggressively mandated. While the ACA’s top goal may have been reducing the number of Americans without health insurance at all, most experts agree that a close second was requiring a greater pooling of financial risk between the healthy and sick, and the young and old. “That is part and parcel of trying to make all of the other pieces work,” said Linda Blumberg, a senior fellow in health policy at the Urban Institute.

Most of the debate over the potential impact of ACA repeal has focused on who might lose coverage if the law is revoked. As the Urban Institute has shown, the coverage expansion under the law has benefited constituencies favorable to each party: Though the number of uninsured has declined most among racial minorities, who mostly vote Democratic, whites without a college education, the cornerstone of Trump’s coalition, ranked second and also scored big gains. The choices about risk sharing affect the total level of coverage, but even more profoundly shape the cost and comprehensiveness of the coverage that the insured can obtain. And on those measures, the costs of repeal could tilt disproportionately against older working-age Americans—a mostly white age group that has become indispensable to GOP electoral fortunes.

Though few subjects may seem more arcane than health-insurance regulation, these contrasting approaches illuminate a core philosophical divide between the parties. The ACA prizes solidarity: It is an intricately interlocked mechanism for sharing the financial risks of medical needs in two respects. First, it shares risk across generations—with today’s young subsidizing today’s old. Second, it spreads risk across any individual’s lifecycle: Under the law, people pay more for health coverage when they are young so they can pay less when they are old. “In many ways under the law the young and healthy are subsidizing the older and sicker on the theory that eventually all of us get older and sicker,” said Sabrina Corlette, a research professor at the Center on Health Insurance Reforms at Georgetown University. “A key policy driver of the ACA is to pool risk as much as possible on the theory that will make coverage more affordable to a greater number of people.”

By contrast, the GOP plans all prize autonomy. They would allow individuals more choice in whether to buy insurance at all or what kind to purchase, and allow the healthy to pay less unless and until they have significant health needs. The price, in policy terms, for that flexibility is accepting wider divergence between the healthy and sick in both the availability and cost of care. Under the Republican plans, “There’s a scenario where people get a cheaper premium and they have more out of pocket cost sharing and more benefit exclusions,” said Christine Eibner, a Rand Corporation senior economist who studies health care. “And if they have a healthy year they look at it and say this is better. But then they could be in for a surprise if there is a catastrophe or they get really sick and they find something is excluded and the cost sharing is really high.”