Jay Cost of Real Clear Politics has an interesting post laying out Hillary's unlikely, but not impossible, path to the nomination. Key grafs:

So, here's my question. What happens to "It's Over" if Clinton pulls a 40-point victory in West Virginia on Tuesday, then follows it up a week later with a 30-point victory in Kentucky? If these states turn out in the same margins that states since March 4th have averaged, that would imply a net of about 290,000 votes for Clinton. That puts her within striking distance of a reasonable popular vote victory. "Over" will be over as we turn our attention to Puerto Rico. ...

The inference I draw is that Puerto Ricans could turn out in huge numbers. If they do, and they swing for Clinton in a sizeable way, the popular vote lead could swing, too. Add 290,000 votes from West Virginia and Kentucky to 250,000 votes from Puerto Rico, account for expected losses in Oregon, Montana, and South Dakota, and you get Clinton leading in many popular vote counts, some of which are really quite valid. If she has one of those leads when the final votes are counted on June 3rd, the race will go on to the convention.

My gut is that the combination of a mild Obama bounce and slightly depressed turnout in West Virginia and Kentucky will make those popular vote margins tough to pull off. And that Obama will get some popular-vote padding out of Oregon. As for Puerto Rico, who the hell knows?

More importantly, in order to have a real shot, Clinton needed to raise doubts among undeclared supers, many of whom privately support Obama--that was the only way to overturn his pledged-delegate win. And the only way to do that was to eat into his coalition. Unfortunately for Hillary, May 6 was her last real chance on that front, and she came up way short.

Long story short: I just don't see it. But, as Cost says, it's not crazy for Clinton to argue that the nomination's still unsettled. And, of course, the better job she does convincing people of that, the better she's likely to do in West Virgina and Kentucky, and the less unrealistic it becomes. (Though it's still pretty unrealistic.) 

P.S. For what it's worth, I probably focused too much on the popular vote when I pronounced Hillary dead Tuesday night. Cost shows that the popular vote isn't completely out of reach (albeit with some funky math involving Florida and Michigan). As I say, what really hurts Hillary is that she's out of opportunities to win on Obama's "home turf."

--Noam Scheiber