OMAHA, Nebraska — Bernie Sanders, who attracted millions of college-aged and young adults to his presidential campaign last year, is following through on a promise he made when he left the race: to promote younger leaders for the Democratic Party.

It may not seem the most likely role for the slightly stooped, white-haired, 75-year-old Vermont senator. But Sanders rallied support Thursday for Omaha’s Democratic mayoral candidate Heath Mello, who’s half his age.

While the Democratic Party searches for a path back to power around the country, Sanders is using his popularity to draw thousands to events to promote next-generation Democrats, though his effectiveness so far is unclear. He’s on an eight-state circuit of rallies with Democratic National Committee leaders, visiting states Donald Trump carried in the November election.

“Maybe, just maybe it’s time to change one-party rule in Nebraska,” Sanders told an audience of more than 3,000 at University of Nebraska-Omaha Thursday, headlining a Democratic Party rally in the GOP-heavy state. “And we can start right here by electing Heath Mello as the next mayor.”

The 17 candidates Sanders’ political action committee has endorsed this year, including Mello, generally reflect Sanders’ call for newer faces in a variety of political positions and have a direct connection to urban concerns or social justice causes. Most are in their 30s or 40s.

The contrast was apparent throughout the university’s Baxter Arena, where supporters waved signs featuring the familiar image of Sanders’ white hair and glasses alongside Mello’s jet black hair and sunglasses.

Mello, a 37-year-old state senator, exuded that youthful theme Thursday. “I just believe the City of Omaha needs a unifying, aspirational vision for the future,” he said.

Some of the candidates Sanders has endorsed are direct products of the his campaign, such as Khalid Kamau, who was elected to the South Fulton, Ga., City Council on Tuesday. The 40-year-old Atlanta-area activist in the Black Lives Matter movement volunteered for Sanders’ campaign last year.

Others, such as Tom Pierrello of Virginia, reflect Sanders’ challenge to the party establishment. The 43-year-old former U.S. House member and adviser to former President Barack Obama is seeking the Democratic nomination for governor against Virginia Lieutenant Governor Ralph Northam.

But Sanders is using his popularity with younger Democrats to chiefly to inspire, rather than directly recruit, the younger faces he says the party needs.

It’s a tricky dance for Sanders, an independent who does call himself a Democrat — rather, a democratic socialist — but sought the 2016 Democratic presidential nomination and aligns with the party’s minority in the Senate.

In the primaries and caucuses he captured 70 percent of the 30-and-younger vote, and those 2 million votes far exceeded the combined totals for Democrat Hillary Clinton and Republican Donald Trump. Among Democratic primary voters alone, Sanders won a solid majority of support from voters ages 45 and younger.