Obama comes up big in North Carolina, and Clinton merely ekes out a win (as of 11 p.m. ET) in Indiana, the combination of which all but ends Clinton's shot at the nomination. Her chances drop 8.4 points to 4.2 percent.

For the past few weeks, Hillary Clinton's candidacy has rested on two possibilities: 1) winning the popular vote and 2) convincing superdelegates that Obama cannot win certain types of voters. (The delegate count is out of reach; she would need at least 70 percent of the remaining delegates to surpass Obama.) Today, Obama exploded both arguments.

The numbers are still trickling in, but it's pretty clear Obama's large win in North Carolina gets him a lot more votes than Clinton's small win in Indiana. If his final North Carolina margin is as high as 14 percent (it's at 15 with 90 percent of precincts reporting), Obama would essentially erase Clinton's popular-vote gains in Pennsylvania. (She netted 215,000 votes in that primary. If 1.5 million people turned out in North Carolina—which looks about right—a 14-point win would net Obama 210,000 votes.) Clinton could still tighten Obama's popular-vote lead by counting votes in Michigan, where Obama wasn't on the ballot, and Florida. But at this point, she doesn't appear able to close the gap. Some superdelegates say they're waiting to see who wins the popular vote. With that metric out of reach, Clinton loses her strongest case to supers.

Her other argument—that Obama is a flawed candidate who can't win white, working-class Democrats—also loses its punch with tonight's returns. The last few weeks have been the roughest of Obama's candidacy, with the Return of Wright, the "cling" thing, and questions about his patriotism. None of that appears to have severely damaged him today. Meanwhile, Indiana is only 8.9 percent African-American. To an extent, demography is still destiny, as it has been in previous contests: Clinton won 60 percent of whites, and Obama won 92 percent of blacks. But Clinton by no means owned lower-income voters—in fact, Obama won the poorest group of voters. Superdelegates may have been concerned that Obama would be abandoned in states like Indiana in the general election—even though there's no evident relationship between winning states in the primaries and winning them in the general. This vote should put that concern to bed.

So, right now her shot at the nomination rests on one thing: Obama messing up big time. Barring this possibility—which certainly is a possibility, but it's out of Clinton's control—she has no arguments left. She may have the most experience; she may still be the best fighter for the middle class; she may be the stronger general election candidate against John McCain. But that's not enough to persuade superdelegates to vote against the candidate who won the pledged-delegate count and the popular vote.

In her speech tonight, Clinton pledged to stay in the race. The question is, why?

For a full list of our Deathwatches, click here. For a primer on Hillary's sinking ship, visit our first Deathwatch entry. Send your own prognostications to hillarydeathwatch@gmail.com.