Donald Trump shocked the political world by winning the 2016 presidential election. There has been much talk of his victories in several Blue states as well as his improved margins among white working class voters. But did Trump really "change the map?" Has he found a new coalition? There is a straightforward way to test this.
Gerald Pomper (1967) first examined continuity and change in presidential elections via linear correlation of state-by-state election results in paired presidential elections. Pomper was interested in identifying realignments. According to Pomper, realignment would be evident via a “change in the parties’ bases of support… the geographic distribution of each party’s vote would be different from the past: traditional strongholds would fall, while new areas of strength would become evident” (1967, p. 539). Such changes or shifts in support would be evident in statistical analyses of the correlation between sequential elections. In short, a break in continuity, as demonstrated by a low level of correlation with preceding elections, suggests realignment. Pomper (1967, p. 540) compared the Democratic party’s share of the total vote by state from 1824 to 1964 and identified five “electoral cleavages” in American history, cleavages that correspond to prevailing scholarship on American party systems.
Like Pomper, I paired successive elections by comparing the Democratic share of the total vote by state to generate correlation coefficients. The state-by-state comparison generates a Pearson correlation coefficient with a low or negative value indicating a disruption or cleavage point and a higher positive value indicating continuity or electoral stability. Figure 1 presents the results. The changes taking place in the parties' coalitions in the late 1970s and early 1980s are evident as is the rather stable electoral period that emerged in 1996 - a period marked more narrow election victories and the emergence of the familiar Red and Blue states.
Donald Trump pieced together an impressive electoral coalition in the 2016 election, a coalition that included traditionally Democratic states like PA, MI, and WI - yet Figure 1 shows the 2016 election demonstrated a high degree of correlation with the election of 2012 – no fundamental changes took place in 2016. Rather Trump was able to achieve narrow victories in otherwise Democratic states. The results suggest that the present path to 270 electoral votes remains both stable and competitive.
Pomper. 1967. Classification of Presidential Elections. The Journal of Politics.