“And what do you mean by “3-way”?
Did we always have real 3rd party candidates??”
There are always third party candidates, but there are some elections where a 3rd party candidate actually has influence.
The last one would have been Ross Perot.
Use the standard where a third party candidate got more than 5% of the vote if you want a limit.
Before that, you have to go back to Ronald Reagans first election, where Andersen grabbing 6% of the vote.
Before that 1972, Wallace grabbed 13.5% of the vote.
1968, not 1972.