Joe Biden defended his age during the Democratic presidential primary debate by saying he would be younger at the end of his first term than Winston Churchill when he left office as British prime minister.

Churchill, who was prime minister during World War II and died in 1965, left office as prime minister in 1955 when he was 80. Biden, who is turned 77 in November, would be 82 in 2024 and 86 in 2028. If elected, Biden, at 78 years and 51 days old, would be the oldest U.S. president ever to occupy the Oval Office

Ronald Reagan, who was widely mocked for his advanced age and did eventually succumb to Alzheimer's, was the oldest person ever elected to the White House. He was 73 years and 274 days old when he won his second term. By the time he left office, Reagan was 77 years and 349 days old. His son Ron said he was suffering from dementia while in office.

Former vice president Biden is the current Democratic front-runner. He struggled with gaining speaking time during the debate.