Presidential and Congressional Vote-share Equations

Three vote-share equations are estimated and analyzed in this paper, one for presidential elections, one for on-term House elections, and one for mid-term House elections. The sample period is 1916-2006. Considering the three equations together allows one to test whether the same economic variables affect each and to examine various serial correlation and coattail possibilities. The resulting three equation model can then be analyzed dynamically, which is done in Section 4. The main conclusions are briefly: 1) There is strong evidence that the economy affects all three vote shares and in remarkably similar ways. 2) There is no evidence of any presidential coattail effects on the on-term House elections. The presidential vote share and the on-term House vote share are highly positively correlated, but this is because they are affected by some of the same variables. 3) There is positive serial correlation in the House vote in that the previous mid-term House vote share positively affects the on-term House vote share and the previous on-term House vote share positively affects the mid-term House vote share. 4) The presidential vote share has a negative effect on the next mid-term House vote share. The most likely explanation for this is a balance argument, where voters are reluctant to let one party become too dominant. Ruled out as possible explanations for this fourth result is any reversal of a coattail effect, since there is no evidence of an effect in the first place, and a regression to the mean, since the positive serial correlation in the House vote implies no such regression. Also, it is not simply voting against the party in the White House, because the presidential variable is a vote share variable not a 0,1 incumbency variable.