OKLAHOMA CITY -- Voter turnout was light early Tuesday after polls opened for the Oklahoma primary election in which several political heavyweights are fighting to replace outgoing Democratic Gov. Brad Henry.

Henry, A Democrat, is term limited and cannot seek another term, and the absence of the popular governor has set off a series of political dominoes in the state.

Attorney General Drew Edmondson and Lt. Gov. Jari Askins each are giving up relatively safe seats to seek the Democratic nomination. On the Republican side, U.S. Rep. Mary Fallin will face state Sen. Randy Brogdon of Owasso and two lesser-funded candidates, Oklahoma City-area businessmen Roger Jackson and Robert Hubbard.

One northeast Oklahoma City precinct reported just three voters in the first hour after polls opened, and a second in the area saw about two dozen.

Helen Grant, a retired postal clerk, said she voted for Edmondson because of his experience and the belief he will help bring jobs to the state.

"When I came up we could go and look for a job, and find one."

University of Central Oklahoma employee Gypsy Hogan said Askins is her choice because of her grasp on complex topics.

"If it is any issue that has to be read more than five pages, and understood, you have to ask Jari," Hogan said.

State Election Board Secretary Paul Xiriax said he had no information on the early statewide turnout. Polls will be open from 7 a.m. to 7 p.m.

With Edmondson and Askins in the governor's race, the seats they left behind are giving Republicans a shot at a statewide sweep in 2010 of major offices in Oklahoma, a state controlled for decades by Democrats.

"I wouldn't say it's likely, but the opportunity is there," said Chad Alexander, a GOP political strategist and former chairman of the Oklahoma Republican Party.

"Barack Obama is the most unpopular Democrat president that we've ever seen in Oklahoma, and every Republican candidate in the state has the wind at their back," he said. "This is a tremendous year for Oklahoma Republicans, and we have opportunities to win where we've never competed before."

Ben Odom, a Democratic political strategist and former vice-chair of the party, said that although the decision by Edmondson and Askins to leave their seats open could expose Democrats to losses for lieutenant governor and attorney general, it also gives the party a legitimate shot at the governor's seat.

"With risk comes opportunity," Odom said. "It's two heavyweights going at it, but the way the campaign has been run, the winner will have a unified party behind them because it hasn't been a vicious primary between the two of them. Whoever loses goes away with their integrity and reputation intact, and I think they'll be back in public service."

Fallin's open congressional seat also has drawn a crowded field -- seven Republicans, two Democrats and two independents. The deep and well-funded GOP field means that race likely will lead to an August runoff.

In the U.S. Senate race, incumbent Republican Tom Coburn is expected to easily fend off two primary challengers -- perennial candidate Evelyn Rogers and retired teacher Lewis Kelly Spring of Hugo. In the Democratic primary, newcomer Mark Myles of Oklahoma City will meet Jim Rogers of Midwest City, another perennial challenger.

Primary races also are set in the 1st, 2nd and 4th congressional districts where the incumbents -- U.S. Reps. John Sullivan, R-Tulsa; Dan Boren, D-Muskogee; and Tom Cole, R-Moore -- all face challenges from within their party. U.S. Rep. Frank Lucas, R-Cheyenne, the state's senior congressman, won't be challenged until November's general election by Democrat Frankie Robbins, whom Lucas defeated with 70 percent of the vote in 2008.

Mostly Republican primary races will be held for several other statewide posts, including lieutenant governor, auditor, attorney general, treasurer, labor commissioner, insurance commissioner and corporation commissioner.

GOP and Democratic primaries will be held for state superintendent, a post incumbent Democrat Sandy Garrett is resigning from after 20 years in office.

Voters also will consider nominees for seats in the Legislature, which Republicans took control of in 2008 for the first time since statehood.

If no candidate secures 50 percent of the vote, a runoff will be held Aug. 24.