We’re going to spend a lot of time over the next 87 days contemplating the possibility of a Donald Trump presidency. Trump is a significant underdog — he has a 13 percent chance of winning the election according to our polls-only model and a 23 percent chance according to polls-plus. But those probabilities aren’t that small. For comparison, you have a 17 percent chance of losing a “game” of Russian roulette.
But there’s another possibility staring us right in the face: A potential Hillary Clinton landslide. Our polls-only model projects Clinton to win the election by 7.7 percentage points, about the same margin by which Barack Obama beat John McCain in 2008. And it assigns a 35 percent chance to Clinton winning by double digits.
Our other model, polls-plus, is much more conservative about Clinton’s prospects. If this were an ordinary election, the smart money would be on the race tightening down the stretch run, and coming more into line with economic “fundamentals” that suggest the election ought to be close. Since this is how the polls-plus model “thinks,” it projects Clinton to win by around 4 points, about the margin by which Obama beat Mitt Romney in 2012 — a solid victory but a long way from a landslide.
But the theory behind “fundamentals” models is that economic conditions prevail because most other factors are fought to a draw. In a normal presidential election, both candidates raise essentially unlimited money and staff their campaigns with hundreds of experienced professionals. In a normal presidential election, both candidates are good representatives of their party’s traditional values and therefore unite almost all their party’s voters behind them. In a …