The conspiracy issue was before the appeals court for 14 months.
Prosecutors allege Terrill, a Republican, offered Leftwich, a Democrat, an $80,000-a-year state job to not run for re-election in 2010.
Prosecutors contend Terrill was trying to help a Republican friend who was planning to run for her Senate seat.
Leftwich, 61, of Oklahoma City, did not seek re-election, but did not get the state job. Brad Henry, then governor, vetoed a reform bill creating the job at the medical examiner's office. Henry acted after the district attorney announced an investigation.
Terrill, 43, of Moore, is no longer in the Legislature. He ran for Cleveland County commissioner last year but lost. He said in August he has been doing consulting work on political campaigns.
Both defendants could be back in court as early as Friday so their preliminary hearing judge can formally order them to face trial.
If convicted, they face up to two years in prison and a $5,000 fine.