In defending their efforts to repeal the Affordable Care Act, Republican leaders in Congress argue that the insurance marketplaces created by the law are failing. They aren’t completely wrong.

Trouble began with faulty websites during the rollout in 2013. Since then, enrollment continues to be below expectations. Obamacare plans often have higher premiums and out-of-pocket expenses than expected. Some markets, mainly in rural areas, may not attract a single insurer in 2018. And insurers that stay are likely to impose double-digit premium increases.

The Republican plan to replace Obamacare would do little to stabilize the exchanges. But there is a better way to provide insurance to the 11 million beneficiaries of Obamacare plans: Allow them to buy into the Medicaid system. For President Trump, “Medicaid for more” would be both good policy and good politics.

Let’s start with a political puzzle. Why has Medicaid become the nation’s largest health insurance program, with over 70 million enrollees, even though both conservatives and liberals criticize it? First, it has surprisingly strong support from hospitals and nursing homes, insurers and states, which receive federal funds to help finance care. Second, since Medicaid is administered in different ways by different states, it cannot be labeled a monolithic national program. Third, its cost is shared among federal, state and local governments. Finally, Medicaid works: It provides access to good-quality care for low-wage Americans and more secure funding for the medical safety net.