The election of Donald Trump into the White House in 2016 sent shockwaves around the world.  A new study from Yale sets out to explore how this occurred.  The research examines the outcomes of the 2012 and 2016 elections in six key states: Georgia, Nevada, Michigan, Florida, Pennsylvania, and Ohio.

Collectively this involved the voter turnout records of around 37 million people, which were merged with precinct-level election returns to try and understand the source of Trump’s success.  The researchers were particularly keen to understand voters who switched from Democrat to Republican.

The analysis revealed that these swing voters were the deciding factor in four of the six states, including the key Rust Belt states of Michigan, Pennsylvania, and Ohio.  Indeed, the researchers argue that these swing voters were more of a factor in Trump’s success than any increase in turnout from the Republican party’s base.

“Despite increasing political polarization, a lot of voters aren’t committed partisans and will cast ballots for a Democrat in one election and a Republican in the next,” the researchers explain. “Turnout certainly matters — the parties benefit from mobilizing their bases — but our study suggests that swing voters were a bigger factor in 2016.”

Electoral change

Studying such change is tricky, not least due to the constantly changing nature of the electorate and the secrecy of one’s actions at the ballot box.  Survey data can help to overcome these gaps to some extent but is still limited in its reach.

“It’s fairly easy to get committed Republicans or Democrats to tell you that they support their teams, but it’s much harder to reach the people who aren’t partisan or don’t vote consistently,” the researchers explain. “Those kinds of voters are important drivers of electoral change.”

So, the researchers relied instead on public records to overcome any shortcomings of survey data or recruitment bias in the sample.  They harvested lists of eligible voters from each state and then matched the voter lists with the election returns at a precinct level.  This allowed them to estimate any switching that occurred between the two elections for each precinct.

Consistent improvement

The data revealed that Trump managed to improve on the 2012 performance of Mitt Romney in each of the states except Georgia.  The balance between the composition of the electorate and the conversion of votes varied by state, but the role of swing voters was consistent in each of the states in terms of explaining Trump’s success.

The role of swing voters was especially pronounced in Ohio, Michigan, and Pennsylvania.  For instance, in Michigan, Trump scored over 100 votes more per precinct than Romney, even as the electorate composition increased the Democratic vote total.  In other words, Trump gained a lot of voters who had supported Obama in 2012.

“In a sense, the difference between composition and conversion comes down to simple math,” the researchers say. “Mobilizing one additional voter adds a single vote to your margin but converting a swing voter adds one to your candidate’s tally while subtracting another from your opponent’s.”

In Nevada and Georgia, the estimated compositional effects were 3 and 1.4 times larger than the conversion effects. The Democrats’ enhanced voter mobilization efforts in Georgia, which are credited with enabling Joe Biden’s 2020 victory in the state, were already producing results in 2016, the researcher explains.

“Georgia demonstrates the importance of voter mobilization,” the researchers conclude. “The Democrats had a massive expansion in registration and an enormous number of new voters entering the political system, which resulted in Trump losing votes relative to Mitt Romney. It set the stage for a surprising win in 2020.”