The Democratic presidential candidates who are backing a healthcare “public option” or “buy-in” that would have the government offer medical coverage to compete with private insurers are offering it as a “pragmatic” alternative to “Medicare for All” — but it, too, will be a long shot.

Recent history illustrates the difficulty of enacting the plan. The public option was in an earlier draft of Obamacare, but it was defeated in 2009 by centrist members of the party. Since then, Democrats have viewed the buy-in as unfinished business on healthcare reform. They argue that a government-offered plan would help in places that have only one private insurer selling coverage, and that competition everywhere would help lower premiums.