Wallace in the end only received something like 13% of the vote mostly from southern states, but for awhile he was polling around 30% and had significant support in many midwestern states and even liberal states like Massachusetts.
I do remember that some of the "Nixon Democrats" I talked to in my day thought Wallace was a backwards joke. I'm pretty sure the "Nixon Democrats" I knew were for Humphrey in '68.
I remember reading that McGovern lacked labor support that other Democrats had. I think he was against "right-to-work" per se, but he voted against repealing Taft-Hartley.