Did President Obama help Democrats win seats in the House of Representatives? A logistic regression that I just completed indicates Obama’s victory in Congressional Districts improved the odds of a Democrat being elected to the House of Representatives by a factor of 94, all other variables held constant.
Data
In order to answer the question I found raw House of Representatives election data in a spreadsheet compiled by David Wasserman
Statistical Method
Using Wassermen’s data I ran a logistic regression predicting a Democratic win (1=yes, 0=no) in the House of Representatives based on three variables:
- PVI_D_or_R, a measurement of how strongly a United States Congressional District leans toward the Democratic or Republican Party, compared to the nation as a whole (1=Lean Democratic, 0=No)
- Incumbent (1 = Incumbent, 0 = No)
- Obama wins the Congressional District (1= Yes, 0=No)
Findings
Complete data was available for 405 observations. Here are the logistic regression results, expressed as odds ratios.
- If a Congressional District leans Democratic the odds of a Democrat winning the district improves by a factor of 23, controlling for the other covariates.
- Obama’s victory in Congressional Districts improved the odds of a Democrat being elected to the House of Representatives by a factor of 94, all other covariates held constant.
- Incumbency was not statistically significant with covariates in the model.
Caveat: It could also be argued that winning House Democrats helped Obama win the district.