The more conspiracy-minded among us might think that Harrison was put in that position in order to guarantee Graham's re-election. Put a more palatable Democrat in his place, and Graham loses.
Leftists have an unhealthy affinity for credentials and people holding them. This explains why they hate the deplorables and other blue collar workers: they don't have enough fancy degrees or accredidations.
Same reason a right-winger wouldn't have shot up a country music concert in Vegas.