Former first lady Jill Biden’s "work husband" and former chief of staff, Anthony Bernal, refused to testify during a Wednesday interview for the House GOP’s probe into former president Joe Biden’s mental decline, making him the second ex-White House aide to plead the Fifth in the investigation. House Oversight Committee chairman James Comer (R., Ky.) said he asked Bernal two questions, both of which the former aide refused to answer : "Was Joe Biden fit to exercise the duties of the president?"