Democrats, also, have struggled to keep up with the times.
The average age of House Democrats at the start of the 115th Congress was 60.1, almost five years older than the House Republican average of 55.5. They also edged out their counterparts in the Senate, where Democrats and independents who caucus with them averaged 61.9 years in age, compared to the Republicans' 61.8. And the party has taken flack for failing to cultivate young talent.
A trio of septuagenarians, Nancy Pelosi, 77, Steny H. Hoyer, 78, and James E. Clyburn, 77, have dominated House leadership for more than a decade.
Democrats did themselves no favors with young liberal voters by putting Hillary Clinton on the ticket last year. She won only 55 percent of the millennial vote, compared to President Barack Obama's 60 percent in 2012, and she underperformed him in almost every swing state.
Democratic strategist Andrew Baumann said Republicans have far bigger problems with young people than Democrats do. They might win elections by focusing on older, white voters for the next few cycles, he said, but that strategy will soon backfire.
"They're going to be in a world of hurt if they have embedded in the minds of these voters what it means to be a Republican, and it's that," Baumann said.
Democrats, for their part, have attempted to rectify some of their mistakes by incorporating liberal issues such as raising the minimum wage, first championed by Vermont independent Sen. Bernie Sanders, into their new Better Deal platform. Democrats also hope to profit from a backlash against Trump.
"This year, more than before, there may be opportunities to engage millennials who usually haven't voted," Baumann said. "In the past, spending a lot of money to make sure independents break our way might not have been the best strategy. But this year is different." ___ (Randy Leonard contributed to this report.)