The NFL alternative failed after one season in 2001.
The president seemingly learned from his dalliance with Vince McMahon's company, using bravado, slogans and nonstop confrontation to craft his image.
Read an exclusive excerpt from the WWE Hall of Famer's autobiography.
The former professional wrestler says he hid the effects of concussions which included seizures.
Multiple concussions forced the former World Heavyweight Champion into a premature exit from the ring.