Reagan didn't bother with MN at all, until the last minute. Air Force One was enroute to CA for election day, and made a quick stop in Rochester, MN.
Mondale won MN by a vote margin so thin that it was less than one vote per precinct (about 1,300 votes, I think). Several third-party candidates each had enough votes to constitute the winning margin.
There were persistent rumors of massive vote fraud in the Iron Range at the last minute to generate enough votes to keep from embarrassing Mondale completely. But, it wasn't worth investigating.
“There were persistent rumors of massive vote fraud in the Iron Range at the last minute to generate enough votes to keep from embarrassing Mondale completely.”
I’ve long heard that story too from GOP activists here in Minnesota. Given the history of voter fraud in Minnesota, I can’t rule it out.