Former Vice President Joe Biden on Thursday got in a tense back-and-forth with an audience member during an Iowa campaign stop after the man claimed the former vice president sent his son Hunter Biden to work for an energy company in Ukraine. "You're a damn liar, man. That's not true," Biden shot back at the man, who said the claims, which have been circulated by some on the right, were backed up by reporting on television. Biden then went on to challenge the man to a push-up contest. "You want to check my shape man, let's do pushups together here,...