Many political scientists subscribe to a “thermostatic hypothesis” of the two-party system suggesting that if one political party gets too hot, it is bound to cool off and vice versa. In presidential politics, I have occasionally heard of the theory of the “eight-year itch,” which suggests that it is rare and difficult for either party to win three presidential elections in a row.
If true, that’s good news for Republicans and bad news for Hillary Clinton, because in 2016 the Democrats will be going for three in a row.
On first glance at recent history, the hypothesis looks good. Start in 1952, the end of the unusual five-term winning streak by Democratic presidential candidates FDR and Harry Truman. The Repubs won two with Ike, then the Dems won two with JFK and LBJ, then the Repubs won two with Nixon. The Dems won in 1976 with Carter. After that, the string of two Reagan victories plus a third Repub win in a row by the first Bush is the only exception (in this period) to the hypothesis that it’s hard to win three in a row. Since then: two Dem terms for Bill Clinton, followed by two Repub terms for George W. Bush, followed by two Dem terms for Obama.
In his “Five Thirty Eight” blog at the New York Times, Nate Silver takes on the hypothesis and trashes it pretty hard. He throws out the thermostat metaphor and adopts the metronome (which, of course, reliably swings only so far in one direction before it must swing back in the other) and headlines his piece: “The White House is not a Metronome.”
Silver (who will soon take his statistical insights from the NYT to ESPN.com) goes back to 1856 (when the current two-party Republican/Democratic lineup was formed), and looks at all 12 instances in which a party that had held the White House for two terms went for a third.
Silver finds that the two-term-incumbent party won four, five or arguably six of those 12 races. (It depends on whether you count the electoral vote winner or the popular vote winner, and on how you deal with 1868, when Abe Lincoln had won two in a row but his second term was served out by his 1864 running-mate Andrew Johnson, who wasn’t much of a Republican.)
Please read Silver if you want the full treatment. But the smartest thing he does, lower down in his piece, is argue for throwing out the close races, such as the kind of vagaries that enabled George W. Bush to be inaugurated in 2001 despite losing the national popular vote. There are several other very close races that are necessary to build up the theory of the eight-year itch.
If there is some kind of big thermodynamic law of how the electorate feels toward a party that has held the White House for eight years, the workings of the law ought not to have to rely on the question of whether to count the dimpled chads.