Part four opens in Chicago prior to the 1960 presidential election, with Joe seeking an alliance with Sam Giancana to secure Illinois votes for Jack. In the White House, the President faces increasing trouble from his Addison's disease, turning to Doctor Max Jacobson for amphetamine shots. Jackie struggles to balance her family with her role as First Lady; she, too, turns to Jacobson. Bobby gears up for his war on organized crime. Jack integrates the Secret Service Presidential Protective Division with the appointment of Abraham Bolden. Frank Sinatra tries to intercede with Joe on Giancana's behalf; Joe rebuffs him but still cautions Bobby. The administration monitors Soviet buildup on the border of East Berlin leading to the sealing of the border. After Hoover plays Bobby a wiretap of Giancana and Johnny Roselli implicating Joe in election fraud, the brothers cut Joe out of Jack's presidency.
