I have no idea. It was also kind of weird that the oath wasn't done until after noon. If I remember correctly isn't the oath usually done just before noon so that you have pledged before you actually become President?
My recollection of the color commentary from 1988 was that the media proclaimed Dan Quayle to be the Acting President for a few minutes before Bush 41 took the oath.
Today the media made it a point that the oath was essentially irrelevant or ceremonial.
Probably Grant. He was rather well known as a sot.