Sanders: If Biden can't handle questions, how can he handle being president?

This video begins with the disastrous Joe Biden interview with CBS News' Errol Barnett, where the slipping former vice president snaps back at the reporter after being asked if he has taken a mental acuity test. Biden's jumbled response includes asking Barnett, "Are you a junkie?"

Former White House press secretary Sarah Sanders wonders how Biden can serve has president if he can't answer relatively easy queries.