Will voter discontent shatter the partisan deadlock in U.S. politics this November?

Heading into the 2016 presidential election cycle, the most influential guide for political journalists was a 2008 book called The Party Decides. Written by four eminent political scientists, it explained that for several decades presidential nominees have effectively been chosen by unelected political insiders, as candidates fight in “invisible primaries” for endorsements by prominent politicians and interest groups. The voters, it argued, tended to ratify these choices and rally around candidates with widespread and prestigious support.

But like John Kenneth Galbraith’s 1967 book The New Industrial State, which argued that big corporations, tempered by big government and big labor unions, determined the course of the economy, The Party Decides turned out to be a better description of the recent past than an accurate forecast of the near-term future. Political science, despite its name, is not a science, and generalizations about presidential elections are risky because there have been so few of them—only 46 since something like the current two-party system sprang into existence in 1832 and only 11 since primaries started dominating the selection of party nominees in 1972. When I was in the political polling business, I was told not to base conclusions on the responses of subgroups comprised of fewer than fifty respondents. Scholars of presidential elections, even if they go back to the days when Andrew Jackson faced off against Henry Clay, have less data to work with than that.