I’m getting mail claiming that when voters are sure their candidate will win, they are less likely to vote. Therefore (these are Democrats writing) I should pipe down. However, this speculation contradicts both human nature and empirical evidence.

First, think about why we vote. Since a single vote basically never swings a race, the rational argument for voting is not strong. Instead, we vote because it is our duty, because we build the habit over time, and because voting makes us feel good. In light of that, the obvious consequence of supporting a winner is increased likelihood of voting – there’s more emotional reward.

Now, some evidence. Consider this post of mine from 2008, The Exuberance of Likelier Voters.

This graph shows outcomes plotted as a function of polling margins. If polls were accurate, the slope of the green line would be 1 with an intercept of 0. But it is not. Indeed, for every 1% of actual margin, only 0.84+/-0.03% is captured in polls*. This underperformance implies that there is a hidden bonus for whoever is ahead. The intercept essentially goes through the origin, so there’s no overall bias toward either candidate.

It seems that this phenomenon could be caused in three ways, not mutually exclusive:

If you live in a state where you are certain that your candidate will win, you are more likely to vote than predicted by likely-voter screens. In the same state, if you support the losing candidate, you are less likely to vote than predicted by likely-voter screens.

Now, I should say that it’s not clear that this idea applies to a national race. But my point is that we don’t have evidence that confidence is a turnout-killer.

Finally, consider the converse. When Donald Trump claims that the election is “rigged,” that tells his supporters that he is doomed. Based on the state-level data above, this might depress turnout.