1996 if Pat Buchanan had run as a third party (Ross Perot still runs and does about as well as he did IOTL)
Buchanan wins 7-8% of the popular vote and throws the entire South to Clinton. note that I believe this would likely be the map if Buchanan had won the GOP nomination as well.
Pat Buchanan did threaten to run Third Party if Dole picked a pro-choice running mate IIRC.