Young voters helped push Democrats to victory in 2018. Can they swing the 2020 vote?

Ashlyn Giroux and Phoebe Mulry held signs on stage for Bernie Sanders when the U.S. senator from Vermont had a rally here in September.

But in between classes at the University of New Hampshire Wednesday, the two freshmen made their way to hear Sen. Elizabeth Warren speak on campus. Both said they've donated $5 to Warren's presidential campaign, although only Mulry has fully committed to backing the Massachusetts Democrat in the primary. Both plan to get more active ahead of voting.

"Elizabeth Warren is my candidate," Mulry said, explaining...