John Edwards, in a move that violates long-standing Democratic campaign protocol, won't say that he'll support the Democratic nominee for president if it is Hillary Clinton. This unusually sour and divisive move is clearly designed to undercut support for Clinton, whom Edwards is targeting in an increasingly bitter fashion in Iowa. As Chris Dodd said in a statement:

This is not the same John Edwards I once knew. Of course, we should all come together to support the nominee. I wonder which of the Republicans John prefers to Hillary?

Barack Obama's response provides a perfect counter-example of how to answer, with charm and grace, the question of whether he'd support Clinton:

"I am a Democrat, and I would support the Democratic nominee,” he said. With a smile, he added, “I intend it to be me.”

UPDATE: Greg Sargent reports that Edwards clarified his position at a press availability, saying:

"I fully expect to support the Democratic nominee, and I fully expect to be the Democratic nominee."

Concludes Greg: "it's still not a full commitment to backing the Dem nominee."

And I just got off the phone with Edwards senior adviser Joe Trippi, who unpacked Edwards' thinking on this question:

All he's saying is he expects to be the nominee. That’s it. It's not any more complicated than that. It has nothing to do with Hillary Clinton or anybody else, as far as I know.

Trippi further clarified why Edwards was reluctant to answer The New York Times' question about supporting Clinton:

He said, "I don't accept the notion that she'll be the nominee."...When you had a whole ten months of people saying, "It's going to be Hillary Clinton or Barack Obama"...the question, if you look at how it was asked, he was saying he doesn't accept the notion that she was going to be the nominee and wasn't going to address that at that point. And my guess is if he were asked about Obama or anybody it would be the same issue.

--Garance Franke-Ruta