Doug Hibbs writes:
Presidential election outcomes are well explained by just two objectively measured fundamental determinants: (1) weighted-average growth of per capita real personal disposable income over the term, and (2) cumulative US military fatalities owing to unprovoked, hostile deployments of American armed forces in foreign conflicts not sanctioned by a formal Congressional declaration of war. At the end of 2007 weighted-average growth of real incomes during Bush’s second term stood at 1.1 percent per annum. If the same performance were sustained for the rest of the term it might barely suffice to keep the Republicans in the White House, other things being equal. However the economy slid into recession at the beginning of the year and per capita real incomes will most likely decline throughout 2008. Moreover, by Election Day cumulative US military fatalities in Iraq will approach 4,500 and this will depress the incumbent vote by more than three-quarters of a percentage point. Given those fundamental conditions the Bread and Peace model predicts a Republican two-party vote share of 46-47% and therefore a comfortable victory for the Democrats in the 2008 presidential election.
Here are the basic data from Hibbs’s bread-and-peace model:
See Hibbs’s latest paper for details on his 2008 forecast.