The graph demonstrates that for each election that a party loses, its nominee get closer to the center of the scale. For example, in 1984 and again in 2004 the Democratic Party had been out of office for only one term. The party nominated Walter Mondale and John Kerry, respectively. But in 1992, having been out of office for 12 years, they nominated Bill Clinton, who was probably more centrist than Mr. Mondale or Mr. Kerry.

Of course, this evidence hardly portends that Rick Perry will win and Mitt Romney will lose. But it does suggest that 2012 could be a year in which the GOP does, to quote Mr. Cohen and colleagues, “test the limits of voter tolerance” by nominating a candidate like Mr. Perry. The authors’ data would suggest that for conservative activists, this is likely their best year to nominate their preferred candidate. A loss to President Obama in 2012 would probably only empower the more moderate “Republican establishment” in 2016.