The principal policy division between Hillary Clinton and Barack Obama involves health care. It’s a division that can seem technical and obscure — and I’ve read many assertions that only the most wonkish care about the fine print of their proposals.

But as I’ve tried to explain in previous columns, there really is a big difference between the candidates’ approaches. And new research, just released, confirms what I’ve been saying: the difference between the plans could well be the difference between achieving universal health coverage — a key progressive goal — and falling far short.

Specifically, new estimates say that a plan resembling Mrs. Clinton’s would cover almost twice as many of those now uninsured as a plan resembling Mr. Obama’s — at only slightly higher cost.

But the big difference is mandates: the Clinton plan requires that everyone have insurance; the Obama plan doesn’t.