Wise bookmakers don't go so much by guessing the results, they follow the betting so that they will win whatever happens, and that is reflected by the odds as they change. So it's basically a poll of the changing expectations of those placing bets.

When bookmakers rely on guessing the results themselves, that's when they are liable to come unstuck.

When Jeremy Corbyn got elected leader the first time, the bookies had to pay out big for the few people who'd backed him at the start, but I doubt if they lost, because of all the people who had backed the losers who looked so much more likely. The same will apply if Trump wins.

Bookies very rarely lose money.