Ronald Kessler reporting from Washington, D.C. — The resignation of David H. Petraeus as CIA director followed an FBI investigation of many months, raising the question of why he was not forced out until after the election. In his letter of resignation, Petraeus cited an extra-marital affair he had been having. “After being married for over 37 years, I showed extremely poor judgment by engaging in an extramarital affair,” Petraeus said in his letter to President Obama. “Such behavior is unacceptable, both as a husband and as the leader of an organization such as ours.” Petraeus, who had a distinguished...