We were reminded once again this week — by The New York Times’ estimable John Harwood — of one of those “rules” that will govern the next Presidential race. In writing of the midterm elections’ impact on the 2016 campaign,—suggesting that a GOP Senate takeover might benefit a Hillary Clinton run — Harwood writes: “American voters have demonstrated their reluctance to award the same political party a third consecutive term in the White House.”

Measured by a glance at recent history, that’s true. But (as NFL officials put it) on further review, there’s a whole lot less than meets the eye. What the record really shows is just how much the fate of the Presidency is governed by the vagaries of chance.

For much of our political history, the “third term” curse was non-existent. During the Republican ascendancy that began with Lincoln’s election in 1860, the party won six straight elections (although it did take some highly sketchy maneuvering in 1876). Later, the White House passed from McKinley to Theodore Roosevelt to Taft, and then from Harding to Coolidge to Hoover. FDR and Harry Truman combined to keep the Presidency in Democratic hands for twenty consecutive years. (Coincidentally or not, in all of these streaks, the death of a President brought a new occupant to the White House.)

The “reluctance” Harwood points to didn’t really begin until 1960. As he puts it: “The combination of fatigue with the incumbent party and rejuvenation by its opposition helped stymie Richard M. Nixon when he sought to succeed Dwight D. Eisenhower in 1960 and Hubert H. Humphrey when he tried to follow Lyndon B. Johnson eight years later. Al Gore lost in 2000 despite President Clinton’s high approval rating and economic record.” In this last half-century plus, only George H.W. Bush was able to win a third term for his party. (Note: in every case, the nominee was the sitting vice-president — a stark reminder of how much more important that office has become in recent decades.)

This account looks convincing — until it’s subjected to a closer look...