In a nutshell, Johnson was a member of a group (sponsored by the Chamber of Commerce, I think) that invited the author of “The Bell Curve” (Murray) to speak to them about education. Murray holds some views on genetics which the far left consider heretical. Read the article for more information.
It is a close race and the donks are afraid of losing a sure Senate seat.
This is designed to peel off the middle, those afraid of being thought racist.
It may work. But, then, again, it may not.