Two-thirds of Democratic voters want someone other than Joe Biden to be their party's candidate for the White House in 2024, according to a New York Times/Siena College poll.

Their top concern: his age.

Joe Biden will turn 80 this year. He's already the oldest American president in history. His predecessor, who wants to run again, is 76.

It's not just the American presidency that's gone grey. House Speaker Nancy Pelosi is 82. Her second in command, Steny Hoyer, is 83. Senate minority leader Mitch McConnell is 80.

But how old is too old? What does age exactly mean in politics? What explains America's aging leadership, and does that really hurt the function of democracy?

Host Zhao Ying is joined by Aaron Kall, Director of Debate at the University of Michigan, Prof. Aubrey Jewett from the University of Central Florida, and Prof. Mark Shanahan from the University of Surrey.