Does congress realign or smoothly adjust? A discrete switching model of congressional partisan regimes

Studies of development and change in partisan fortunes in the US emphasize epochs of partisan stability, separated by critical events or turning points. In this paper we study partisan electoral changes in the US Congress using the method of Markov switching. Our estimates are based on election changes from 1854, roughly the date of the establishment of the modern incarnation of the two-party system, to the present. For the Senate, we estimate partisan balance both from 1856 and from 1914, the period of direct elections. Our discrete-state method performs better than one based on smooth cycles, and is more consistent with the existing theory.We use the Markov switching method to estimate an underlying unobserved state parameter, ‘partisan regime’. The method allows the direct estimation of critical transition points between Republican and Democratic partisan coalitions. Republican regimes characterized House elections during three periods: 1860 through 1872, 1894 through 1906, and 1918 through 1928. Senate results were roughly similar. Every recession caused a realignment prior to 1932, but since then none has.For the Senate, the two-state model does not fit adequately. We estimate a three-state model in which a Republican regime dominated from 1914 through 1928; a Democratic regime characterized the period 1930–1934, and a Democratic-leaning regime characterized the period 1938 to the present (1936 is a transition year).The driver for historical realignments up to 1930 seems to have been economic distress, at least for the House. Each recession before 1930 is associated with a realignment, but after 1930, no recession produced a realignment. Since then, however, economic downturns have not led to realignments. We speculate that better economic management since World War II, resulting in shallower recessions, is the cause. For the Senate, however, we detect only one fundamental regime shift: that during the Great Depression.