Conservatives view the many ACA provisions that promote risk sharing—from the mandate on individuals to buy coverage to limits on how much insurers can vary premiums based on age—as forms of government coercion that raise prices. In response, the principal Republican alternatives would all unravel that risk sharing. Many younger, healthier people might gain in that process. But even some conservative analysts agree the big losers would be older, working-age people not yet eligible for Medicare. That age group is predominantly white and now solidly Republican. Whites older than 45 provided most of Trump’s votes, and almost three-fifths of House Republicans represent districts where the median age exceeds the national average.

Each of the Republican plans shift costs from young to old first by repealing the ACA’s individual mandate. The mandate, though widely disliked, underpins the law’s more popular requirement that insurers sell coverage to all consumers at comparable prices, regardless of prior health conditions. Without the mandate, people could wait until they are ill to buy coverage, knowing that insurers would have to sell to them. That would produce unsustainable losses for insurers. Only by requiring people to buy insurance when they are healthy can the law guarantee it will be available when they are sick. Through the mandate, the young stitch the safety net for the old.

To maintain the requirement on insurers to sell, while eliminating the mandate on individuals to buy, the leading GOP plans instead create a “continuous coverage” rule. The rule says insurers must sell, at comparable prices, to anyone who has maintained insurance without a break in coverage, regardless of their health status. By advantaging patients who maintain coverage, the rule is intended to incentivize people to purchase insurance without the mandate’s absolute requirement.

The problem is that the Republican plans eliminate the ACA’s requirement that all insurance policies provide robust minimum benefits like hospitalization and maternity care. Under a continuous-coverage system, that means healthy people could buy inexpensive skeleton plans and only shift to more inclusive coverage when they get sick, knowing that insurers must sell it to them. Christine Eibner, a senior Rand Corporation economist, said that scenario may prevent insurers from offering comprehensive plans to anyone on the individual market, because the only people buying them would be those with greater health needs. “You have a significant risk that this [entire] insurance market becomes bare bones,” she said.

That risk is compounded by another key GOP proposal: allowing any insurance policy approved in one state to be sold in any state. The ACA already allows interstate sale when all the affected states agree. But no insurer or state has pursued such cross-border sales, largely because out-of-state companies can’t easily compete with local insurers in building an affordable network of doctors and hospitals.