Is there a seemingly unmovable 30% to 40%?

After reading Tara Westover's Educated and now reading Rising Out of Hatred by Eli Saslow, I see the pattern as to why 30% to 40% follow the current occupant in the White House. 

Check out the clip of Derek Black the subject in Saslow's book on The Daily Show: https://tinyurl.com/y4hcd88z