Its not a bad idea, and its not an EITHER/OR proposition.
Trump will not lose a single upper midwest state he won in 16, and he’ll most likely win MN as well in 20.
He isn’t just targeting this list of states, he will be very active in all the states he won in 16, and won’t lose a single one of them and will take a few more at least, that are on this list.
I think that the wisdom of my strategy involves resources,time and stamina.Although he's likely to be well funded next year (2016 was the first time I donated to a Presidential campaign,next year will be my second) he's not likely to have unlimited funds. And I'd wager that the Rat nominee will be very well funded because the Rats' hatred will be greater next year than it was in '16.
As for time and stamina...it's a big country and even employing my strategy would be grueling...particularly given that he now has a day job.
TV ads in the states mentioned would be OK...if funding allows. But visits? Maybe not.
The MFers counting the votes in mn are Soros Democrat Steve Simon (sos) and pos AG Keith Ellison. Uphill climb :p