Ezra Klein, contra Brad Delong, argues that steadily dropping the age of Medicare eligibility is a bad strategy for expanding health-care coverage:
First, if you can't pass Medicare-for-All, what makes you think you can pass Medicare-for-More? The industry stakeholders won't be confused about where this process is going. Nor will Republicans. The opposition will react with exactly the fury you'd see directed against a single-payer proposal. But far fewer people will benefit. The opposition, in other words, would mirror the opposition to single-payer, but the potential support is a lot smaller.
The second problem is that this probably reduces, rather than expands, the constituency for health-care reform. You're seeing this now with health-care reform. As Friday's Gallup poll showed, seniors are the least supportive constituency for changes to the health-care system. They worry it'll mess with the comfortable arrangement they already have.