President Donald Trump has mocked his Democratic rival for letting his mask hang off his ear when he delivers speeches. Speaking to rally-goers in Pennsylvania, Mr Trump said: "Did you ever see a man who likes a mask as much as him? "He has it hanging down. Because it gives him a feeling of security. If I were a psychiatrist, right, you know I'd say: 'This guy's got some big issues. Hanging down. Hanging down'."