Trump says Biden has 'obligation' to take a cognitive test, presidency requires 'stamina' and 'mental health'

President Trump joins Fox News medical contributor Dr. Marc Siegel for an exclusive interview on'Tucker Carlson Tonight.' In an interview Wednesday with Fox News medical contributor Marc Siegel, President Trump boasted about his cognitive test performance and said presumptive Democratic presidential candidate Joe Biden should take the test. "In a way he has an obligation to," Trump said, adding that the presidency requires "stamina" and "mental health." Trump said he took the test to prove to the media that he was fit to serve in the presidency after reports supposedly questioning his cognitive ability. Trump has used the argument that Biden is too old to run for president as a cornerstone strategy in his presidential campaign against the former vice president.