So imagine she wins the nomination. Obama's supporters will be vexed, to say the least. Clinton, who hoped not only to win the nomination in a cakewalk but to enter the general election as a plausible moderate and centrist, will be put in the position of having to placate many of the most important left-wing constituencies of her party: wealthy liberals, young people and, most of all, African-Americans.
This means that at precisely the moment she needs to move right toward the center, she will need to move left to shore up an angry base. In other words, the Democratic Party would nominate the most polarizing candidate possible (roughly half the country already says it will never vote for her), who will have to become even more polarizing in order to appease aggrieved Obama voters.
Meanwhile, she would be facing a GOP candidate with a sterling record of winning the support of moderates, independents and even Democrats. Both McCain and Clinton would probably enter the race with, say, 47 percent of the vote already in their pockets. So, who would be better positioned to win a majority of the undecided middle-of-the-roaders? Hillary Clinton, the scandal-plagued Assassin of Hope, or John McCain, Mr. Bipartisan War Hero?
Of course, this isn't necessarily the most likely scenario. Obama still seems poised to best Clinton. But I wouldn't put it beyond the Clintons to sabotage Obama in the general election, if for no other reason than to keep Hillary's chances for 2012 alive.
No one knows what will actually happen. But for the first time in a while, Republicans have reason to hope that the gleam of light on the horizon might - just might - be a new dawn and not an oncoming train.