Schlesinger’s feat inspires the present study. The authors argue that there are cycles in American ideology. Roughly every 12 to 15 years since 1854, American voters have oscillated between preferring Democrats or Republicans in national office, with a complete cycle every 25 to 30 years.²

The basis of this claim is nakedly empirical. In their first table, the authors perform elementary run tests to demonstrate that “both the House and the Senate have far fewer runs (i.e., fewer partisan switches) than” randomness would allow.³ That is, one party tends to control the House (or Senate) over several elections, then the other party gets a turn.

It’s not enough to show that changes in partisan control are non-random, though, to explain Schlesinger’s uncanny predictions. So the authors turn to a specialized technique, spectral analysis, to see whether there is a consistent cycle length causing these runs. They analyze House, Senate, and presidential elections separately, then all together. All four analyses yield a consistent result: A half-cycle (i.e. change in partisan dominance) of around 13 years, a full cycle (i.e. return to original party) of around 26.

This empirical finding influences our understanding of partisan realignment in two ways. First, and most importantly, it revives a literature severely criticized by Mayhew (2002). Realignments do occur. Nonetheless (and second), the authors carefully point out that their evidence suggests a sort of tidal ebb and flow, not a punctuated equilibrium (or “tipping point”) model in which realignments occur suddenly following a “critical election.”⁴

They explain these findings with a formal model that has four main moving parts:

1. Parties prefer to promote policies as close to their ideal point as possible;
2. To win election, parties will move as little as necessary toward the median voter;
3. The party in power enjoys certain advantages of incumbency that shield it on election day;
4. Voters tend to react negatively to the ruling party’s proposals. The median voter becomes more conservative when liberals are in charge, and more liberal when conservatives are in charge. (See Stimson 1991 and 2004.)

The first two considerations create a centrifugal-centripetal tension, simultaneously pulling the party toward the median and toward extremism. Over time, the second consideration overpowers the first.

The latter two points also conflict, reflecting a tension among voters between valuing incumbency and desiring change. When a party first acquires power, its newfound incumbency advantage helps it at first. But as time goes on, the advantages of incumbency are overwhelmed by changes in the electorate’s mood.

Together, these two pairs of considerations create a cyclical pressure.