I’m planning to vote for Obama in tomorrow’s primary, but one thing eats at me: his wholly inadequate health care plan. Paul Krugman of the New York Times has written several columns about it, and today’s is one of the most incisive.

Clinton’s plan requires everyone to have health insurance; Obama’s doesn’t. And no matter how affordable his plan makes health insurance, some people still won’t enroll. History has shown this to be true. And if people choose not to enroll until they develop health problems, this raises premiums for everyone else.

According to one paper Krugman cites:

[A] plan without mandates, broadly resembling the Obama plan, would cover 23 million of those currently uninsured, at a taxpayer cost of $102 billion per year. An otherwise identical plan with mandates would cover 45 million of the uninsured — essentially everyone — at a taxpayer cost of $124 billion. Over all, the Obama-type plan would cost $4,400 per newly insured person, the Clinton-type plan only $2,700…. One plan achieves more or less universal coverage; the other, although it costs more than 80 percent as much, covers only about half of those currently uninsured.

Krugman concludes:

If Mrs. Clinton gets the Democratic nomination, there is some chance — nobody knows how big — that we’ll get universal health care in the next administration. If Mr. Obama gets the nomination, it just won’t happen.

Clinton and Obama have debated health care a few times. But I don’t recall Obama ever explaining why his health care plan is better than Clinton’s.

It nags at me.

[Update: some rebuttals are collected here.]