There are four million uninsured adults ages 55 to 64—12% of the population in that age group. One in four is in poor or fair health, and most have low incomes—making the average $415 per month premium for health insurance (for single coverage) out of reach for many. Those with preexisting conditions face being denied coverage altogether.

Enter the idea of a Medicare buy-in for people in this age group who have no other access to health care coverage. Medicare usually kicks in at 65, but an early buy-in would allow someone as young as 55 to enroll in the program. Depending on the program’s ultimate design, the premiums would cost several hundred dollars—higher than what those over 65 pay—and cover the same services current Medicare beneficiaries receive.

The new idea isn’t new—it’s been around for a decade—but Senator Max Baucus (D-MT) revived it in his Call to Action: Health Reform 2009 white paper.

“The program wouldn’t be permanent, but rather a way for older workers to access care immediately while we work to get the Health Insurance Exchange—a one-stop health coverage marketplace where Americans can easily compare and buy affordable plans—up and running,” wrote Baucus, the Senate’s Finance Committee chairman, in a blog on the National Journal’s Web site.

Once that’s in place, he says, those who enrolled in the buy-in could stay with that program or they could buy insurance through the Exchange. (To read responses to his comments by other experts in the field, go to the National Journal, a nonpartisan Washington, DC–based magazine.)