OKLAHOMA CITY (AP) - Six Republicans entered Tuesday's Oklahoma primary confident that their party could win an open congressional seat currently held by a Democrat. And three Democrats went into the election hopeful they could retain the seat in a state that has grown overwhelmingly conservative.

Three incumbent Republican congressmen faced challengers within their party Tuesday, while Democrats will pick challengers in two districts.

Drawing the most attention is the fight for a seat currently held by U.S. Rep. Dan Boren, D-Okla.

Polls are open from 7 a.m. to 7 p.m.

A primary runoff will be held Aug. 28 if no candidate captures more than 50 percent of the vote.

The only statewide election on the ballot Tuesday is a Republican primary for a full term on the Oklahoma Corporation Commission.