In 2016, when polls, pundits and forecasters were all predicting a certain victory for Hillary Clinton, the PRIMARY MODEL was practically alone in predicting Donald Trump’s victory. It did so as early as March 7 that year, putting his chance of winning at 87%. http://primarymodel.com/2016-forecast-full. The Primary Model is the brainchild of Professor Helmut Norpoth, Stony Brook University.
It is a statistical model that relies on presidential primaries and, in addition, on an election cycle as predictors of the vote in the general election. This year the model has been calibrated to predict the Electoral College vote.
For the record, the PRIMARY MODEL picks the winner of 25 out of 27 elections since 1912, when presidential primaries were introduced. The misses are 1960, one of the closest presidential elections, and 2000, when the late count in Florida handed Bush the victory; still Al Gore wound up winning the popular vote.