US President Joe Biden has announced that he will be running for a second term in office. Biden, now 80, is already the oldest American president in history. If he wins the presidential election next year, he will be 86 by the time he leaves the White House. His political rivals, and even some of his supporters, are now asking the same questions. How old is too old to be president? At what age is a person still fit to be the individual with the nuclear codes? Today, Peter Hartcher, political and international editor of The Sydney Morning Herald and The Age, on whether Joe Biden’s age could determine his political future, and how other world leaders have been embraced - or rejected - as they entered their ninth decade.Subscribe to The Age & SMH: https://subscribe.smh.com.au/See omnystudio.com/listener for privacy information.