With more than 1,700 of the state's 2,220 precincts reporting, CBS declared Clinton the winner over Sen. Barack Obama of Illinois, 55 percent to 30 percent.

Arizona's McCain captured 38 percent of the vote, good enough for CBS to project him the winner. Former Arkansas Gov. Mike Huckabee won 33 percent while former Massachusetts Gov. Mitt Romney earned 24 percent.

State Election Board Secretary Michael Clingman said he expected 550,000 people to vote, or "a little over 30 percent from both parties," the Daily Oklahoman reported.

Forty-seven delegates are at stake for the Democrats. In the GOP race, 41 delegates are up for grabs.