The Democratic Primary has reopened the electability debate among Democrats on who is best positioned to beat Trump in 2020. Do they gamble on a progressive candidate or hedge with a center-left nominee?
Intuitively, both strategies seem sensible. A progressive candidate who excites the base can increase turnout among loyal Democrats. On the contrary, a moderate candidate who reaches swing voters has wider appeal. The evidence makes it clear overall that a less extreme candidate with a broadly popular agenda will best position Democrats to win. In particular, the base’s insistence on progressive purity through a focus on contentious issues like race and immigration is likely to lower Democrat’s chances and drive voters towards Trump.
Political science research shows that in congressional campaigns, extreme candidates systematically do poorly. They increase turnout among the other party’s base, more than compensating for turnout of their own supporters, which implies a progressive candidate would lower Democrat’s chances to beat Trump.
This is because of the motivations that drive people to vote. In Identity Crisis: The 2016 Presidential Campaign and the Battle for the Meaning of America, political scientists John Sides, Michael Tesler, and Lynn Vavreck show that the reason Trump was able to win was because he harnessed issues core to the identity of many White voters without a college degree: he tapped into their social and cultural attitudes around race and demographic change.
Precisely because most voters make decisions on the basis of social identities and partisan loyalties, not fixed policy positions, as political scientists Christopher Achen and Larry Bartels argue in Democracy for Realists, extreme candidates will fail to tap into the motivations of voters beyond their core base. And as other research shows, negative partisanship and dislike of the other party has increasingly become a core motivation of voters, further suggesting extreme candidates will drive the other side’s base to turnout.
If voters tend towards basing decisions on social/identity issues and are motivated by negative partisanship, this raises a question about Presidential elections. Because they see higher turnout than other national and local elections, and have higher levels of candidate name recognition, the pool of swing voters is smaller. That suggests, with increasing polarization in the electorate, that presidential elections could be solely about motivating one’s base to turnout more than the other side’s base and that the swing voter is dead.
We can show, however, that the swing voter strategy is still key to winning elections with the Congressional Cooperative Election Study, a nationally representative sample of the electorate in the last three presidential elections. We use that data to split the electorate into groups based on partisan identity: Democratic-Base, Democratic-Other, Republican-Base, Republican-Other, and Swing Voter.
To understand how influential the base and swing voter groups could be in 2020, we start with the six states that had a vote margin of less than two percent in 2016: Florida, Michigan, Minnesota, New Hampshire, Pensylvannia, and Wisconsin. These states were close enough that small changes could have swung them either way, and they are likely to be swing states in 2020.
When evaluating whether a campaign should target base or swing voters, there are three variables that matter: likelihood of party support, turnout, and geography.
Looking at the likelihood of voting Democratic, it is clear that the Democratic-Base is far more loyal to the Democratic party. Getting Democratic-Base voters is more effective than turning out the same number of swing voters.
On turnout we see that the Democratic-Base in 2016 voted at higher rates than Swing Voters, but the Democratic-Base turned out at a lower rate than the Republican-Base. If the two bases had voted at equal rates, that would only have swung Michigan and Pennsylvania, which wouldn’t change the outcome. Democratic-Base enthusiasm appears to not be a reason Democrats lost. Indeed, comparing 2012 to 2016, Democratic-Base turnout increased.
For geography, the number of non voters in each category is far larger than the vote margin by state, which supports either strategy. There are, however, far more swing voters than base voters, suggesting they are easier to target. This is true even when splitting swing voters into two categories: those that didn’t vote (Swing Voter-Non Voter) and those who voted Republican (Swing Voter-Republican).
Putting together the important factors, likelihood of party support favors the base strategy, turnout favors the swing voter strategy, and geography is a toss up.
To assess all factors simultaneously, we show two heatmaps to re-simulate the 2016 election under different scenarios in the six key states above. Red means Republicans win under a given scenario while blue means Democrats win.
The first focuses on a base motivation strategy, showing on the x-axis increases in Democratic-Base turnout and on the y-axis increases in Republican-Base turnout. The second shows the swing voter strategy where the x-axis represents increases in Swing Voter-Non Voter turnout while the y-axis shows getting Swing Voter-Republicans to instead cast a ballot for Democrats.
Under the base strategy, Democrats would need the votes of at least 11% of Democratic-Base non voters in key states. This is quite a large increase given already high turnout within the base. Furthermore, appealing to the Democratic-Base with extreme candidates increases turnout among the Republican-Base, making it hard to maintain enough net votes. And this holds in reverse too where the Democratic-Base is likely to turnout regardless of the Democratic nominee to vote against Trump because of the strength of negative partisanship in motivating turnout.
Many more combinations in the swing voter strategy result in Democrats winning. Gaining 5% of Swing Voter-Non Voters or 1% of Swing Voter-Republicans in key states would change the election. Fewer Swing Voter-Republicans are required because stealing Republican voters essentially lowers the vote margin by two as it simultaneously increases Democratic votes and lowers Republican votes.
It is clear that a strategy opting for swing voters is better as there are more swing voters in key states, and smaller changes in getting them to turnout and support Democrats can dramatically change election odds.
This means focusing on both crafting a moderate candidate profile and constructing a policy platform with mass appeal, especially in terms of swing voters who otherwise might support the Republican party. Whether it is the energizing figure of Bernie Sanders or the more centrist Joe Biden, moderation in speech and policy ambition will be essential.