“Young people are constantly signaling what’s next and what’s possible,” Mr. Robinson said. “And while there’s some love for Biden, but sometimes you’re in a relationship because you’re comfortable and it’s what you know.”

Another Texas Southern student, Christopher Anwuri, 22, said the generational differences in how black voters saw the primary were fueled by opposing theories of political change: incrementalism versus immediate upheaval.

“This generation is looking for an instant, quick fix for problems,” he said. Older black people, meanwhile, think “these things need to take time.”

It also comes back to Mr. Obama, and the long shadow he casts over national Democratic politics, particularly in black communities. Older black voters invoke his name in deference, and cite his embrace of Mr. Biden as something that helped him win the trust of skeptical white voters in 2008.

To younger generations, many of whom were in high school or younger at the time, Mr. Obama’s achievements exist on their own. Their first memories of Mr. Biden stem from his highly meme-able vice-presidential years. They are also more likely to hold his long and at times controversial record — on criminal justice, school segregation and the Clarence Thomas hearings, among other things — against him.

Jayla Lee, 19, said older black voters “like Biden because he was with Obama, and they feel like since they could trust Obama that means they can trust him.”

“But the things we endure are not the things they endured,” Ms. Lee said. “And I’m looking for someone who can change the things that affect me.”