The Role of Incumbency and National Voting Patterns in State Legislative Races
I base my analysis of legislative races in Louisiana almost entirely on two factors: 1) Presidential voting patterns within districts; and 2) Whether or not an incumbent is on the ballot.
1. Presidential voting predicts legislative voting
Voting patterns in national and state elections are not all that different. True, “blue states” sometimes elect Republican governors (e.g., Massachusetts and Maryland), and “red states” elect Democratic governors (e.g., Louisiana). But consider, for example, the fact that the party whose presidential nominee carried it in the most recent presidential election holds 86 percent of districts in the Louisiana House of Representatives (i.e., Democratic legislators in Clinton districts and Republican legislators in Trump districts). The rate is even higher (92 percent) in the Louisiana Senate.
Similarly, the Republican vote share in the most recent presidential elections (since 2012) predicts Republican vote share in contested legislative races in Louisiana at a nearly one-to-one rate. The figure below shows the relationship between Republican vote shares for president in the district (in the most recent presidential election) and the Republican vote share in the next legislative race for the 40 legislative races contested by both parties since 2012. A one-point difference in the vote share for the Republican presidential nominee is associated with a one-point difference in the Republican vote share in the next legislative race, on average.
2. Incumbents in the Louisiana Legislature almost never lose.
In the past 20 years, Louisiana has had 535 legislative elections with an incumbent on the ballot. The incumbent candidates won 507 (95 percent) of those contests. This rate even includes two incumbents who lost only because redistricting forced them to run against two other incumbents (meaning at least one incumbent had to lose in each race). The rate is similar in each chamber – 94 percent in the House and 96 percent in the Senate.
There are, of course, many factors that also matter for what happens in these elections – not least of which is the quality of the candidates and the campaigns they run. Incumbency and national voting patterns in a district do not predetermine the outcomes of each legislative election. Nevertheless, they are both highly predictive and provide a straightforward way to measure the political landscape within each district.