Age is an underappreciated factor in the Democratic Party’s internal divisions.

When fault lines emerged during the 2016 presidential primary, young people fell overwhelmingly on the side of Sen. Bernie Sanders, I-Vt., over Hillary Clinton. While Sanders himself is 76, his support among young people helped him give Clinton a scare heading into the convention. One survey estimated Sanders won more than twice as many young votes as Clinton did over the course of the nominating contest.