In the 1966 election, Hall finished a close third in the Democratic primary for governor. Four years later, he defeated incumbent Republican Governor Dewey F. Bartlett in the closest gubernatorial election in state history, and took office only after a recount confirmed his victory. As governor, he championed education and transportation issues. His administration issued a landmark public policy analysis book of Oklahoma's education system entitled "Measuring up and Moving On." Hall and his appointees to the state highway commission and turnpike authority were committed to expanding the state's roads. During his term as governor, the state drastically expanded the vocational technical system of facilities offering low or no cost training certificates for residents. As governor, he signed into law the Oklahoma Income Tax Act, which enacted Oklahoma's income tax code. Hall's administration and policy initiatives were opposed and attacked on a regular basis by the state's largest newspaper, the Daily Oklahoman, and its powerful publisher, billionaire Edward Gaylord. Gaylord had supported Hall's opponent, former Governor Dewey Bartlett.
Unsuccessful re-election bid
Hall was unsuccessful in his quest for re-election in the 1974 election. He obtained only 27 percent of the vote, a third-place finish in the Democratic primary. He trailed U.S. Congressman Clem McSpadden and State Representative and Oklahoma Baptist University professor David Boren, who eventually won the nomination and the general election over Republican Jim Inhofe.
Charges and retirement
Three days after leaving office in 1975, Hall was indicted on federal racketeering and extortion charges, in a conspiracy involving Hall and Oklahoma Secretary of StateJohn Rogers willfully steering State of Oklahoma employee retiree funds to investment funds controlled by Dallas, Texas, businessman W. W. "Doc" Taylor. At Hall's trial, Rogers testified that he became an informant after Hall offered him a bribe. Hall was convicted of bribery and extortion, and became the first Oklahoma Governor to be convicted of criminal acts committed during his tenure. After exhausting all appeals, he served 19 months of a three-year sentence at the Federal Correctional Institution, Safford. Upon his release from prison in 1978, he was disbarred by the Oklahoma Bar Association, which effectively prevented him from practicing law in Oklahoma. Leaving the public spotlight, he moved to La Jolla, California, where he worked in real estate and other ventures.
Return to Oklahoma
On February 13, 2007, Hall made his first appearance in the state of Oklahoma since he left office over thirty years before. He appeared at the Oklahoma History Center to help launch a new exhibit that features all of the Governors of the State of Oklahoma. Hall remarked that it was "like coming back to heaven." He authored a memoir, 2012's Twisted Justice: A Memoir of Conspiracies and Personal Politics which features his recollections of his time in office, and his reflections on his prison sentence and subsequent career.
Death
Hall died at a San Diego area hospital on May 6, 2016. He had earlier been implanted with a pacemaker and had expected to be discharged, but then developed a blood clot that ultimately went to his brain and caused a fatal stroke. He was 85.