Lynn Vavreck for NYT’s The Upshot:

Despite the robust record of these models, they didn’t get much attention leading up to 2016. Mr. Trump was such a nontraditional candidate — in his fund-raising; support for atypical G.O.P. positions on trade and on protection of Social Security and Medicare; minimal advertising; and seemingly arbitrary ground game — that politicians and analysts alike thought he would knock the election out of the equilibrium where structural factors like party and the economy mattered. “If it were a normal year” or “with any other candidate” were common refrains that came as fundamentals models were dismissed.

In actuality, the state of the nation’s economy — growing slowly — was predicting a very close election in 2016: a contest that either party could win.

For all of the exceptionalism of 2016, the outcome was remarkably typical. The final vote share was very close, as the low growth rate and lack of an incumbent suggested it would be.