Former President Donald Trump’s pending return to the White House could alter the very nature of Medicare, the nearly 60-year-old federal program. More than half of Medicare beneficiaries are already enrolled in plans, called Medicare Advantage, run by commercial insurers. Based on Trump’s campaign positions and previous policies, that proportion is now expected to grow – perhaps dramatically – for a number of reasons Trump and many congressional Republicans have already taken steps to aggressively promote Medicare Advantage.

And Project 2025, a political wish list produced by the conservative Heritage Foundation for the next presidency, calls for making insurer-run plans the default enrollment option for Medicare. Such a change would effectively privatize the program, because people tend to stick with the plans they’re initially enrolled in, health analysts say. Trump has repeatedly tried to distance himself from Project 2025, though the document’s authors include numerous people who worked in his first administration.

Conservatives say Medicare beneficiaries are better off in the popular Advantage plans, which offer more benefits than the traditional, government-run program. Critics say increasing insurers’ control of the program would trap consumers in health plans that are costlier to taxpayers and that can restrict their care, including by imposing onerous prior authorization requirements for some procedures. “Traditional Medicare will wither on the vine,.