> Following the primary election in September, a poll on October 20 showed Humphrey leading 35% to Coleman (34%) and Ventura (21%)
That's pretty far behind. But I'm not going to research this because you're the one trying to make the point, and you need to defend your position that it's a useful one, not switch topics to alternative voting systems.
If people followed your suggested voting tactic then Humphrey or Coleman would have been governor. They didn't, and ended up with Ventura. Not only was he a plurality winner, but from what I can tell he was a Condorcet winner too.
The voters got who they wanted. Not what the polls said was the lesser of two evils as you would have had them choose.