Here's what's going to happen:
Trump knows he's going to lose, but his ego can't handle that. His brain is wired to think "it's not possible people CAN'T want to vote for me". Therefore, his auto-defense mechanism to save face is to claim the election is rigged. Trump has millions of supporters, and because their candidate is not winning, they'll buy into the whole "there's cheating going on!" thing. Once the polls close on Nov. 8th and the votes are counted showing Hillary the winner, we're going to see riots in major cities, and I'm betting the National Guard is going to get involved.
After that, we're going to see rumblings of a police state, how America is turning into Nazi Germany, and we're going to have a lot of political discord for a few months.
The smoke will clear sometime mid-next year, and the "reasonable" Republican leaders will realize all of the infighting is what created Trump's candidacy, and they'll start prepping a proper candidate for 2020. There will also be a Republican witch-hunt for senators/congressmen that supported Trump and they'll be chastised and distanced. "I didn't support Trump" will become the new "I didn't vote for the Iraq war".
Against any other decent R. candidate, Hillary would be losing by a landslide due to all of her baggage, but she has the advantage of being against a completely inappropriate and unqualified ass-clown, so she's basically being handed the election. We'll probably elect a Republican President next time around (unless Hillary really kicks some ass), and there will be a lot less fighting/violence next time around.