Donald Trump is a candidate who divided his own party more deeply than any presidential candidate has before.

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.

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.

Donald Trump is a candidate who divided his own party more deeply than any presidential candidate has before.

If Pat Toomey of Pennsylvania wins, for instance, it will tell Republicans that their own brand hasn't been hurt too badly by [Donald] Trump's negatives.

[Hillary] Clinton has also struggled with key groups of voters.

If [Donald] Trump wins narrowly, Democrats can blame the loss on FBI director James Comey, who inserted himself late in the campaign in an unprecedented way.