Republican voters are coalescing behind [Donald] Trump, but many Republican elected officials still say they can't support him.

Well, it's possible that the new infusion of ad money against Donald Trump kept his margins in Kentucky and Louisiana down a bit. But we're also seeing something that we've never seen in 100 years, which is we are seeing the crackup of a major American political party.

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

If Donald Trump wins, it will be a seismic event.

If [Donald] Trump loses narrowly, it will make it much harder for the GOP to unify. Under that scenario, the Trumpists are likely to argue that the election was lost because the Republican establishment failed to rally around the choice their own voters made.

The Senate is the big prize. Until recently, Democrats felt confident they could get the four seats they needed to take back control if [Hillary] Clinton is in the White House and Vice President Tim Kaine held the tie-breaking vote.

The aftermath of this extraordinary election [2016] could be just as surprising as the race itself.