HNN:  Historians are agreed that presidential debates have had little effect on the outcome of elections, moving the needle in just a few cases by a mere 1 percent.  But 2016 may be the exception. 

The third and final presidential debate has ended, and it can now be said: Hillary Clinton crushed Donald Trump in the most effective series of debate performances in modern political history.

The polling tells the story. As Nate Silver notes, on the eve of the first presidential debate, Clinton led by 1.5 points. Before the second, she was up by 5.6 points. Before the third, she was winning by 7.1 points. And now, writing after the third debate — a debate in which Trump said he would keep the nation "in suspense" about whether there would be a peaceful transition of power, bragged about not apologizing to his wife, and called Clinton "such a nasty woman" — it’s clear that Trump did himself no favors. Early polls also suggest Clinton won.

And it’s not just the presidential race. Betting markets now predict Democrats will win the Senate. Polls have started showing Democrats in striking distance of the House. The GOP has collapsed into a mid-election civil war, with the party’s presidential nominee openly battling the speaker of the House.