That’s just one more example of how congressional actions and attitudes on health care reform are inconsistent. Republicans think subsidies based on bids is an excellent way to reform Medicare, but they don’t laud the Affordable Care Act for adopting the same approach. When it comes to the A.C.A., of course, Democrats supported this mechanism, but they’ve opposed it when it comes to Medicare reform.

Obamacare’s creation of the insurance exchanges and subsidies to expand coverage was a move leftward, supported by Democrats and opposed by Republicans. Anything that relies more heavily on private Medicare options would be a move rightward, and it would probably be opposed by Democrats and supported by Republicans. Such is Washington.

It’s worth noting that progressives are also concerned that this plan might erode traditional Medicare. It could do that because, for a variety of reasons, private plans are likely to bid lower than traditional Medicare. If people have to pay more for traditional Medicare, relative to private plans, they’re likely to leave it, weakening that arm of the program.

The second main idea included in some premium support plans is to further protect the government from rapidly growing expenditures by explicitly capping the growth in subsidies. This could be layered on top of the bidding approach. It would work like this: Plans bid, and the government picks the average or second lowest. Then the government makes sure it doesn’t pay a predetermined amount more than last year — a growth cap.

This kind of cap on subsidy growth is an even more contentious issue. As anyone who follows health care spending knows, it has grown significantly faster than inflation for the past several decades. Putting a more restrictive cap on growth will make budget projections look better. The problem is that such action assumes that there are ways we haven’t previously figured out to reduce Medicare spending without reducing benefits, reducing reimbursement or increasing cost-sharing.

Progressives fear that, given our inability to control health care spending in other ways, this would most likely wind up transferring more and more of the cost of health care onto older Americans themselves. Many would be unable to afford care. The same problems we’re seeing with underinsurance and cost-related access barriers in the private insurance market could become more prevalent.

The entire point of premium support is to rely on the market to innovate and come up with more efficient ways of providing health care and health insurance for it. So one cannot say in advance how it would keep costs below a growth cap.