The mental ability and age of the United States presidential candidates took centre stage on the campaign trail on February 10, as former President Donald Trump accused President Joe Biden of lacking the mental capacity to be president, following a report that suggested Biden was suffering from memory lapses.The issue was thrust front and centre again after Special Counsel Robert Hur, a former U.S. attorney in Maryland during Trump’s administration, said in his report that he chose not to bring criminal charges against Biden following a 15-month investigation into his handling of classified documents because the president cooperated.Hur said the Democratic incumbent would be difficult to convict and described him as a “well-meaning, elderly man with a poor memory” who was not able to recall to investigators when his son, Beau Biden, died.Trump, at a rally in Conway, South Carolina, said Hur’s report showed Biden “is not fit to serve as our commander in chief.”Trump – who faces four state and federal criminal trials, including one for mishandling classified documents – is close to clinching the Republican nomination, and the prospect of a likely general election rematch with Biden in November.In a White House appearance on Thursday night, Biden angrily denied Hur’s allegations about his memory, saying, “My memory’s fine.”