Republicans in Congress and the Trump administration repealed the penalties associated with the Affordable Care Act’s individual mandate in the tax act that passed in December. Now they need to replace the mandate with something that will address rising premiums and command broader support. Automatic enrollment into health insurance plans is a good place to start.

A replacement for the mandate is needed because the A.C.A.’s insurance rules are still in place. Those rules, which enjoy bipartisan support, protect the sick by requiring insurers to charge the same premiums to all consumers of the same age without consideration of their health status. The mandate was supposed to encourage the healthy to stay continuously insured, through a federal tax assessment for every month without coverage, even though they could drop coverage and later acquire it when needed, without paying higher premiums. With enforcement of the mandate ending in 2019, more healthy people may leave the A.C.A.’s exchanges, driving up premiums even faster for those who remain in the market.

Automatic enrollment counters the natural human inclinations toward myopia and inertia. Many people do not plan adequately for contingencies, either because they don’t want to or because they lack the resources to do so. Further, the natural disinclination toward taking action means some consumers will not jump through the hoops necessary to sign up for benefits even if they find what is being offered attractive.

Employers use automatic enrollment today in their pension plans, and it works. Firms place workers into plans and set default contribution rates for them. Workers retain the right to change their rates or their investment funds, or to stop contributing altogether. More than two-thirds of all firms sponsoring pension plans use automatic enrollment to increase participation among workers who do not opt in to the plans on their own. The percentage of firms with at least an 80 percent participation rate in their defined contribution retirement plans has increased to 64 percent in 2014 from 50 percent in 2010, largely because of automatic enrollment.