The window was there for a brief moment. The problems that have plagued Barack Obama over the past month or so provided Hillary Clinton with the chance to do something she had yet to do--mount a comeback in a state that had already been conceded to her opponent. Had she done so, had she somehow squeezed out a victory in North Carolina or even made the race close, it would have been a crippling blow to the Obama campaign.
But it didn't happen. Instead, Barack Obama swept to an easy victory in the Tar Heel State, leaving Indiana, where Clinton needed a strong victory, as the evening's nail biter. Whatever momentum Hillary gathered with her 10-point Pennsylvania triumph is now gone. Only the cold reality of mathematics remains, and it is not her friend.
It is quite possible that the Super Delegate dam will now burst, and Obama will be the presumptive nominee even before the next state votes. But it doesn't matter. The race is over. For better or worse, Barack Obama will be the Democratic nominee for President of the United States. Whether or not he is the strongest candidate (and it says here that he isn't) no longer matters. The sound you hear this evening is Hillary Clinton's window closing.
At this point, there is no need for her to continue seeking the nomination. As my seven or so readers know, this blog has generally argued for Clinton's candidacy on the basis of electability. But the question is now moot. Senator Clinton should withdraw from the race and allow her colleague to begin his general election campaign.
There is no longer any benefit in hanging around.