Who votes when? Midterm and presidential voters differ primarily by age.

Voters in American congressional midterm elections are widely viewed as demographically less representative than those in presidential elections - older, whiter, wealthier, and more educated. Using Current Population Survey data from 1994 through 2024 as well as voter-file data, we test this conventional wisdom and show that it is partly right but too broad. The key difference between midterm and presidential electorates is age: midterms sharply underrepresent young citizens and overrepresent older citizens compared to presidential elections, while differences between the elections by race, income, and education are much smaller. Midterm voters are, above all, older voters.