In 1968, the Nixon campaign was concerned that President Johnson would make progress before the election at the Paris peace talks to negotiate an end to the war in Viet Nam. The Nixon campaign reportedly tried to stall any progress by convincing the South VietNam government not to join the peace negotiations as they would get a better deal from a Nixon administration.
In the book October Surprise, historian Gary Sick alleged that the 1980 Reagan campaign contacted the Iranians through William Casey to encourage them not to release the hostages until after the election, again with the promise of a better deal. I believe that there were congressional hearings about these charges although I don't know what the results were.
In 1968, the Nixon campaign was concerned that President Johnson would make progress before the election at the Paris peace talks to negotiate an end to the war in Viet Nam. The Nixon campaign reportedly tried to stall any progress by convincing the South VietNam government not to join the peace negotiations as they would get a better deal from a Nixon administration.
There is one very important difference. South Vietnam was an ally of they United States. The Soviet Union was the putative enemy of the United States. Also incumbent DemocRAT president was trying to undermine (backstab) an ally to help the DemocRAT Vice-President and presidental candidate Hubert Humphrey, while the Republican presidential candidate was promising to help an ally.
In 1984 the former DemocRAT president was trying to enlist the help of the number one enemy of they United States to try to defeat the sitting President of the United States. If that had occurred during wartime it would have been treason.