I think the Democrats are sick of presidential dynasties as Republicans are. My opinion only, but McCain wins big over Hillary.
I think an underreported factor is the growing tension between blacks and latinos. Blacks have lost their long-held “largest minority” standing, and Hillary’s win in TX showed how pivotal the hispanic vote is and will continue to be. Watching Hillary assiduously court the latino vote, perhaps tapping someone like Bill Richardson for her VP, savvy blacks may wise up, refuse to reliably fall in line behind the Obama killer, and stay home this November.