[Please see updates below.] I am sorry to run this into the ground, following this and this. But ...

To say this as plainly as possible: Mitt Romney's refusal to release his tax returns is untenable.

He can't stick with this policy if he hopes to win.

Even if Romney had an unshakable high-principle reason for refusing, it is obvious that in the specific circumstances of this year's campaign his stand is hurting him far more than it helps. Which is why people presumably rooting hard to get Obama out of the White House -- including Bill Kristol, George Will, Matthew Dowd, Haley Barbour, and the Republican governor of Alabama -- have made this same point.

And it is all the more damaging because of Romney's reputation as a calmly, cautiously rational, non-shoot-from-the-hip operator. Three messages I've just seen on this theme:

1) From a veteran correspondent who has written about national and international affairs for more than 50 years, and whom I first met when he was covering the Jimmy Carter campaign:



As I see it, there is only one conceivable reason why Mitt Romney won't release his tax returns and move on. It is that their disclosure would reveal a shocking level of avoidance that would jeopardize his presidential hopes.



2) From a veteran lawyer and policy-expert who worked on Capitol Hill in the late 1960s and has been involved in campaigns and politics since then:



I assume the reason he hasn't released his tax returns is that, effectively, he can't; the substance and/or appearance of the returns would be such that the story wouldn't blow over after a few days, it would blow him up within a few days. Isn't this the only explanation for his non-release of the returns that makes sense?



3) An item just now from John Cassidy on the New Yorker's site, which does what I was going to encourage someone on our site to do this afternoon. Cassidy goes into the sorts of things that might be in a tax return that could be worse than enduring heat for refusing to disclose. His summary is here.