The last known stolen presidential election was 1960.
And we know who did that one.
But I suspect 1976 was stolen too, although uncoordinated among the big city political machines.
The race was close, and it didn't take much to change the real outcome.
A political boss in Chicago creating 50,000 "votes" there, a ward hack in Cleveland creating 5,000 "votes" there, a precinct worker in Boston creating 25,000 "votes" there, &c., &c., &c., and it all added up enough to get the Incompetent One "elected."