The winner's margin of victory also matters. If it's a squeaker, that will make the lessons learned for both parties much murkier.

Even if [Donald] Trump concedes, some of his supporters have promised to take up arms against [Hillary] Clinton.

Obama's even keel sometimes comes across as aloof or even cold.

The [Hillary] Clinton campaign's recent travel schedule shows how seriously it takes this problem. She and her surrogates have held rallies in cities like Philadelphia, Detroit and Cleveland, trying to boost turnout among African-Americans.

If they can get 15 or higher, it will be a very bad night for House Speaker Paul Ryan. Ryan twisted himself into a pretzel by endorsing but not always supporting Donald Trump. Now, he's facing the prospect of a slimmer majority, with fewer moderates. Conservative members in the Freedom Caucus have already sent warning shots threatening Ryan's tenure as speaker.

Yes, the presidential race is very close, and some public polls show it getting closer as we go into the final hours, but in one sense it's actually been stable for months.

African-American voters are not nearly as enthusiastic about [Hillary] Clinton as they were about [Barack] Obama.