OKLAHOMA CITY — Primary voters complained about the nation's economy as they headed to the polls Tuesday to whittle a field of six candidates for Oklahoma governor and decide their party's nominee for the state's top post.

Democrats Attorney General Drew Edmondson and Lt. Gov. Jari Askins, two popular incumbents, are squaring off on one side, while U.S. Rep. Mary Fallin faces state Sen. Randy Brogdon of Owasso and lesser-funded Oklahoma City-area businessmen Robert Hubbard and Roger Jackson in the GOP primary.

Voters also will decide nominees in races for U.S. Senate and Congress, state House and Senate, and eight statewide posts, including five open seats.

If no candidate captures more than 50 percent of the vote, a primary runoff will be held Aug. 24.

Fallin, who is vacating her congressional seat, was unable to vote for herself Tuesday after being called back to Washington for a vote on a supplemental funding bill for the war in Afghanistan.

By noon, voter turnout had been average, according to Oklahoma Election Board Secretary Paul Ziriax. About 25 percent of registered voters were expected go to the polls.

"What we're seeing on average is about what you'd expect for a primary election," he said, adding that he expected about 500,000 votes to be cast.

There are just more than 2 million registered voters in the state. Polls opened at 7 a.m. and would close at 7 p.m.

Donnie Andrews, a 49-year-old police officer who voted at the Providence Church in the conservative Oklahoma City suburb of Moore, said he was most concerned about the economy and "the well-being of our nation."

"I was planning on retiring, but not with the economy the way it is," Andrews said.

Ken Patrick, 56, a retired General Motors worker, said he is a longtime Republican with a bit of an independent streak and expressed displeasure with all incumbents.

"As far as I'm concerned we should throw them all out of office."

Fallin was the first woman and first Republican ever elected lieutenant governor in Oklahoma, a post she held for 12 years before running in 2006 for the open 5th District congressional seat. She has been the favorite on the GOP side since she announced her candidacy but has been battling a pesky challenge from Brogdon.

A conservative state senator from Owasso, Brogdon has embraced the tea party and attacked Fallin in television ads that accuse her of "liberal compromises" for things such as her 2008 vote to bail out the nation's financial industry.

The owner of a heat-and-air company, Brogdon has served eight years in the state Senate.

Edmondson and Askins both are vacating relatively safe seats to try and keep the state's top political prize, the governor's seat, in Democratic hands.

A Vietnam veteran and a one-term House member in the 1970s, Edmondson has served four terms as attorney general. Before that, he was elected three times as Muskogee County district attorney, which he hoped would give him a boost in Democratic strongholds across eastern Oklahoma. The Edmondson name also is a staple in Oklahoma politics — Edmondson's father is a former U.S. congressman, his uncle was elected governor in 1958, and his brother is chief justice of the Oklahoma Supreme Court.

Askins also has impressive political credentials, having served as a special district judge in Stephens County, a member of the pardon and parole board and 12 years in the statehouse before she defeated then-House Speaker Todd Hiett for lieutenant governor in 2006.

Askins also enjoyed a last-minute endorsement from former University of Oklahoma football coach Barry Switzer, a state icon who gave underdog Brad Henry a boost in his 2002 governor's race.

Edmondson has raised the most money among all the candidates, amassing nearly $2.6 million in contributions through July 12, according to the most recent campaign finance reports.

Askins topped the $2 million mark by loaning her campaign $675,000 during the most recent reporting period, records show.

Fallin reported raising more than $2.4 million, while Brogdon has raised about $392,000.

Jackson and Hubbard both reported raising less than $15,000.