 During a phone interview with MSNBC on Monday, Biden tried to address concerns coming from his own party about mental fitness. He said those Democrats wanting him to drop out should run against him and challenge him at the DNC in August. The White House is facing a barrage of questions about the mental fitness of President Biden. Monday's press briefing became contentious, following a report that a Parkinson's disease expert visited the White House eight times over an eight-month period.