Senate races have tightened along with the presidential race. Watch to see how many Republican Senate candidates outperform Donald Trump - and how many hang on to their seats in states that he loses.

Jeb Bush was supposed to be the establishment candidate, but he didn't catch on. And the extraordinary thing about this Republican primary is that the establishment, moderate wing of the party has sidelined itself. They're not coalescing around one candidate as they have in the past.

If [Hillary] Clinton can come close in those two traditionally red states, it will be because of the diverse, educated populations around Atlanta and Phoenix. And it will be a sign that Arizona and Georgia are on their way to becoming the new battleground states.

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

No one is predicting that the Democrats will get the 30 pickups they need to take back the House majority.

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

You have [Donald] Trump and [Ted] Cruz battling it out, and the moderate establishment candidates like Chris Christie or Jeb Bush, Marco Rubio, John Kasich - they have formed a circular firing squad.