The big fact about the 2008 primary battle was that supporters of Hillary and Obama were genuinely stoked about their candidate. Historically stoked on two important levels: both in the scale of their enthusiasm and that both candidates' supporters felt -- accurately -- that they were on the verge of making history, a heady expectation. By the end of the battle there was a lot of anger and acrimony. But it was mainly because both sides were going to take being denied so hard. And that's why the divisions were relatively easy to overcome.
You just can't say anything like that about this primary cycle. The hunger to beat Obama is overwhelming. But the polls -- especially by their inconstancy -- have shown little strong affection for any of the folks on offer. And that suggests an outcome like the old saw about academic politics where the politics are so bitter precisely because the stakes are so small. That portends growing damage rather than mounting enthusiasm in a drawn out battle.