In 1982, when Gray decided not to run for re-election, Leftwich ran and won the primary, runoff, and general elections.
He decided to forgo re-election in 1988 in order to run for State Corporation Commissioner, but lost in the runoff to Charles Morgan.
After his career in the Oklahoma House of Representatives, Leftwich was executive vice-president of the Del City Chamber of Commerce.
Although Leftwich was frequently mentioned as a candidate for the Democratic Party nomination for Governor of Oklahoma in the 2002 election, he declined to enter the race and supported Brad Henry.
Following his death from cancer, his widow Debbe Leftwich won the special election on December 9, 2003 to succeed him.