Slate's Trailhead takes up the idea that a long primary will be good for Democrats:
You hear the idea batted around that Democrats want this race to be over (perhaps among Obama supporters more than others). Republicans have chosen their man, the thinking goes—it’s time for Dems to wrap this up.
But that doesn’t take into account the extent to which the longest primary in history has energized the Democratic Party. Take this estimate that Texas’ primary turnout is expected to be more than 3.6 million on the Democratic side. Compare that with the 2.8 million Texans who turned out for John Kerry in the 2004 general election. I thought Clinton was delusional when she said in her acceptance speech tonight that she thinks Democrats can win Texas in the general. But look at those numbers.
By that logic, the longer the primary drags on, the more the party benefits. Democrats will probably turn out in record numbers in Wyoming and Mississippi next week, and again in Pennsylvania in April. And in swing states (Pennsylvania, North Carolina), energizing new Democratic voters could make a huge difference in the general.
I don't see it. To start with, at least some of those voters are being energized by the fact that they don't want the other candidate to get in; to the extent that that's how you're motivating them, it doesn't help you in the general. Also, the Republicans are taking this time to rest, rebuild, and fundraise; the Democrats are spending record fundraising hauls on bashing each other. By the time they come out of the primary, McCain will have had a nice long stretch to recuperate from the trail, and can begin attacking his opponent; whoever the Democratic nominee is will have to do the equivalent of running a marathon and an Iron Man triathlon back-to-back. And it may well come down to a superdelegate showdown that will leave some part of the base angry and demoralized. Sure, Humphrey almost beat Nixon after a nasty primary battle. But McCain is no Nixon.
That is not to say that McCain will win. But I don't think that this is going to be good, or even neutral, for the party.