Tuesday's results replicated much of the Democratic race during the last two months. Hillary Clinton once more showed her strength and Barack Obama's weakness among white working class voters in Midwestern swing states, while Obama proved his hold on young and college-educated voters in states where a new post-industrial economy has developed, and where college-educated voters make up about half of the Democratic electorate.

For Obama, the question will be how to capture enough of these white working class voters in November to defeat Republican John McCain. For Hillary Clinton, the remaining question is retrospective. Her success in states like Pennsylvania, Ohio, and Kentucky only puts into relief the question of why--after having been the prohibitive favorite to capture the nomination--she had already lost the nomination to Obama by the time she had begun to articulate her own message of change.

A big part of the reason, extensively reported by my colleague Michelle Cottle, is that she and her campaign made glaring organizational errors. Clinton wasn't prepared for a protracted nomination battle; and when it became apparent that her staff wasn't either, she didn't act quickly enough to replace them (as Ronald Reagan did in 1980). But another part of the reason for Clinton's failure is political: how she ran initially, and how she ran against Obama.

-MORE--