(KTEN) — The polls are now open across Oklahoma for early voting in the Republican and Democratic primary elections.

Polling places are open from 8 a.m. to 6 p.m. on Thursday and Friday, and from 8 a.m. to 2 p.m. on Saturday.

Primary Election Day is Tuesday, June 28; polls will be open from 7 a.m. to 7 p.m.

Incumbent Republicans Gov. Kevin Stitt and Sen. James Lankford are both facing challengers in their reelection bids.

At the same time, voters can select their candidate in a special election for the seat of retiring GOP Sen. James Inhofe.

Oklahoma's five U.S. House seats are also in contention. Fourteen GOP candidates are running in District 2, which encompasses much of eastern Oklahoma including Durant, Madill, Tishomingo, Antlers, Atoka, Idabel and McAlester.

The District 2 seat is currently held by Markwayne Mullin, who is a Republican candidate in the special election to replace Sen. Inhofe.