Are There Cycles in National Politics?

Are there predicable, cyclical patterns in national politics?  In particular, does the proportion of the Democratic/Republican vote share for the U.S. president or does the seat share in Congress or other parliaments rise and fall over extended periods of time?  If so, are such cycles regular, what are the cycling periods, and have periods changed over time?  In joint work with Bernard Grofman (University of California, Irvine) and Thomas Brunell (University of Texas, Dallas), we use spectral analysis to test for the presence and determine the length of those cycles, showing that regular cycles do, in fact, exist – with periods in the U.S. of 25-30 years that conform to those predicted by the Arthur Schlesingers, Sr. and Jr., for swings between liberalism and conservatism.  In an effort to identify the forces that might drive such cycling, we offer a voter-party interaction model – a negative feedback loop -- that depends on the tensions between parties’ policy and office motivations and between voters’ tendency to sustain incumbents while reacting against extreme policies.  We find a plausible fit between the regular cycling that this model projects and the time series of two-party politics in both the U.S. and Britain over the past century and a half.  Finally, we report work on wavelet analysis by other researchers that permits the assessment of changes in cycle length over time.  Analysis hints that cycle lengths in the U.S. may have shortened in recent decades.