Has Democrat John Fetterman found a way to beat the reality-TV politician?

Whether it’s Ronald, Donald or Arnold, Americans are all too familiar with the phenomenon of the second-tier celebrity turned politician. So when the TV doctor Mehmet Oz decided to run for Senate in Pennsylvania, his background as a B-lister seemed well suited to the role.

As he proudly notes in his official biography, Oz has won Emmys, has written eight bestsellers, and was featured on six seasons of The Oprah Winfrey Show. He is a master of traditional media. But now the daytime TV star is facing a Democratic opponent who has...