Chris Bowers makes a fair case for why Hillary Clinton ought to drop out if she loses Indiana and North Carolina. Bowers urges readers to make this idea the normative Dem position going forward.
Here is the "but."
As a matter of strategy, so long as the superdelegate option is available to Clinton and so long as the earned delegate/popular vote disparity is close, she will probably avail herself of the argument. So the counter to this would be to get the superdelegates off the fence -- perhaps the next project of the Democratic netroots.
My other sense is that the other vulnerable spot for the Clinton campaign is the sense that Bill's legacy and Hillary's Senate future are perilously close to being driven by factors out of her control.
Can you imagine, or envision, a Democratic/Netroots' based Senate challenge to Clinton in four years?
Incidentally, if Clinton wins Pennsylvania, Indiana and North Carolina, then what? The party is already employing a version of the Mondale argument -- he went into the convention losing primaries in 1984 -- as if that was among the main reasons why Ronald Reagan beat him so soundly in the fall. I doubt that argument will work later.