Dirty tricks and October Surprises are nothing new.
Four days before the 1924 general election, the conservative Daily Mail published a letter they claimed was written by a senior Russian Communist (Grigorii Zinoviev) to the British Communist Party. These were their headlines:
The letter made it clear that the socialist Labour government were little more than puppets of the Russians. The letter outraged and terrified the country, already in a state of red-terror. It contributed, at least to some degree, to Labour losing the election. Those undecided voters, you know?
Only problem was, the letter was a forgery. A fake. Possibly produced and definitely backed by the Intelligence communities of MI6 and MI5. (International and domestic, respectively.)