When JFK was assassinated, Speaker of the House John McCormack of Massachusetts became next-in-line for the presidency. At that time, a vice-presidential vacancy could not be filled until the next presidential election. One editorial said that this was a terrible situation because “[a]bility and vigor, sad to say, are found only in vestigial traces in the Speaker.”
How old was McCormack? 72. Younger than three modern Presidents (Reagan, Trump, and Biden).