The questions about Biden's age and fitness are reminiscent of another campaign: Reagan's in 1984

The age question for presidential candidates is more than four decades old. President Ronald Reagan answered it with a pledge to resign if he became impaired, and later with a clever joke that reset his campaign from a stumbling debate performance to a 49-state landslide and a second term.

The audience roared, even Democratic Vice President Walter Mondale laughed — and Reagan's reelection was back on track.