Is Obama Helping Hillary to Win the Election and Become President?
If President Obama were up for re-election this year he would be expected to win due to the well known incumbency effect. He’s not up for reelection, but is it possible that his incumbency benefit somehow extends to Hillary Clinton, the candidate who is running on behalf of President Obama’s party?
With DataSplash as our handy data exploration solution, we took all of the available 2016 data from RealClearPolitics and generated a linear fit aka “running a regression” to see if Obama’s job approval rating is associated with Hillary Clinton’s performance in contemporaneous polling. Grab the house-made data set here!
The explained variable is the average difference between Clinton’s polling percentage and Trump’s polling percentage on a given day. If Hillary averaged 47 and Trump averaged 44 in the polls on a certain day, the variable called hillary_avg would take a value of 3.
The regression indicates that Clinton does get something like a significant incumbent advantage, even though she isn’t an incumbent! The data indicates that for each point increase in President Obama’s job approval rating, Hillary receives an increase of about .477 to her lead in the polls.
Hillary maintains a strong lead overall according to these data, winning by an average of about 5.3 percentage points over Trump. DataSplash allows us to easily make predictions who Hillary would fare if Obama’s approval ratings tanked.. As shown below, the Prediction feature in DataSplash shows us that if Obama’s job approval rating went down to 35.5%, the best estimate of Hillary’s lead would be about -1.08. That is Trump has a 1 percentage point lead! At a 37.75% Obama approval rating, Hillary’s lead is basically zero. For those who are interested in significance, we can’t rule out that Hillary has no advantage over Trump, base on the standard 95% confidence interval, displayed in brackets below.