Looks from Google Groups like Presidential elections were first discussed on Usenet in 1984 (although there's discussion of Reagan and Carter as early as 1981, so it might've been 1980 if Google's archive doesn't go far back enough).
https://groups.google.com/forum/#!search/reagan$20before$3A1984$2F01$2F01%7Csort:date
It always blows my mind to see to see people talking about stuff 30+ years ago on internet forums that were basically the same as they are today.
I noticed that Mondale actually won the 1984 poll on net.politics, by a landslide: 79 votes vs. 49 for Reagan.
https://groups.google.com/forum/#!searchin/net.politics/mondale$20reagan$20poll/net.politics/rKEhNxazX6U/xT2mEJOBRmsJ