What to watch for in the Biden-Trump presidential debate

U.S. President Donald Trump and Democratic presidential nominee Joe Biden participate in their second 2020 presidential campaign debate in 2020, at Belmont University in Nashville, Tenn. (REUTERS/Jonathan Ernst/File Photo)

The two oldest candidates ever to run for U.S. president meet on June 27 for a televised debate unlike any other. One accuses his rival of being unhinged and a danger to democracy, while the other accuses his opponent of being senile and corrupt.