Is this too old for the job? Joe Biden claims that having lived a long life is an advantage for a president — and Donald Trump is in no position to contradict him.
78 or 81: the age of America’s next leader
Record breakers: Joe Biden and Donald Trump are already the USA's oldest presidents. Glossary
White House - The official residence of the US president, in Washington DC. Burnt by British troops in 1814, it was rebuilt and painted white to hide the smoke stains.
Republican Party - Also known as the Grand Old Party or GOP, it is one of the USA's two major political parties. Its first president was Abraham Lincoln. It sits on the right of the political spectrum.
Neuroscientists - A scientist who studies the brain and the nervous system.
Winston Churchill - The British prime minister during World War Two, and later from 1951 to 1955.
Mahatma Gandhi - An Indian political activist and lawyer (1869-1948), who emphasised passive resistance.