Polls are opening at county election boards across the state for the first of three days of early voting ahead of Tuesday's primary election.
Beginning at 8 a.m. Thursday, voters can cast their ballots for several races, including Democratic and Republican primaries in the race for Oklahoma's open U.S. Senate seat. Only Republicans and Democrats can vote in primaries in Oklahoma.
Early voting will continue at county election boards from 8 a.m. to 6 p.m. on Friday and from 9 a.m. to 2 p.m. on Saturday.
Governor Mary Fallin and U.S. Senator Jim Inhofe are among Republican incumbents facing a primary challenge.
This is the first year that early voting on Monday was eliminated, a request from the Oklahoma Election Board to help election workers better prepare for Tuesday's election.