OKLAHOMA CITY — A sparse turnout is expected statewide in Tuesday's primary election in Oklahoma because of the lack of serious races at the top of the ticket.

About 1.8 million Democrats and Republicans are eligible to vote, but less than 30 percent of them are forecast to go to the polls.

"I'm predicting it will be light statewide because there's no contested top-of-the-ticket races," said Mike Clingman, state Election Board secretary.

He said the turnout will most likely be less than a similar election in 2004, when about 500,000 went to the polls. In that primary, Republican Tom Coburn won a fierce three-way U.S. Senate battle on his way to victory in the general election over Democrat Brad Carson.

"Obviously we have local county races and a couple of state Senate races with active primaries where you may have larger activity," Clingman said.

Several candidates are running for some House and Senate posts, setting up probable runoff contests on Aug. 26.

Democrats in the House are eagerly awaiting the general election, predicting they will make gains in the 101-member body, which Republicans now control, 57-44.

Republican officials say they will at least hold their own in the House and will most likely take over the Senate for the first time in history.

With 24 Democrats and 24 Republicans, the Senate is the only tied legislative chamber in the country.

In Tuesday's U.S. Senate primaries, both incumbent Republican Jim Inhofe and Democratic hopeful Andrew Rice face nominal opposition from underfinanced candidates.

Inhofe's primary foes are newcomers Ted Ryals of Moore and Dennis Lopez of Thackerville and Evelyn Rogers of Tulsa, who has run several times for federal posts.

Rice's only opposition is Jim Rogers of Midwest City, who ran for lieutenant governor two years ago and has run previously for the Senate. Rogers got less than 6 percent of the Democratic primary vote for the Senate in 2004.

None of the Senate candidates except Inhofe and Rice filed campaign contribution reports with the Federal Election Commission. Inhofe had raised more than $5 million and Rice more than $1.4 million.

Inhofe, known as a tough campaigner, advertised heavily on television after filing for re-election in early June, billing himself as a stubborn advocate for Oklahoma interests.

Rice, first-term state senator from Oklahoma City, stressed his faith in TV commercials and said Inhofe has "lost his way" after 22 years in Washington. Rice said he turned to public service after his brother was killed in the terrorist attack on the World Trade Center in 2001.

The only other statewide race on the primary ballot is for the Republican nomination for the right to oppose Democrat Jim Roth for an unexpired two-year term on the Corporation Commission. The GOP candidates are state Rep. Rob Johnson and former administrative law judge Dana Murphy. Roth, an appointee of Gov. Brad Henry, is unopposed.

Expected to easily advance to the general election are incumbent U.S. Reps. John Sullivan of the 1st District, a Republican, and Dan Boren of the 2nd District, a Democrat.

Republican Reps. Frank Lucas of the 3rd District, Tom Cole of the 4th District and Mary Fallin of the 5th District did not draw primary opposition.

In the 1st District, businesswoman Georgiana W. Oliver and Iraq protest leader Mark Manley vie for the Democratic nomination to face Sullivan; Boren is opposed by Kevin Coleman of Grove in the 2nd District and Bert Smith and Steven L. Perry are matched in a Democratic primary in the 5th District. Smith is making his third bid for the post, which Republicans have held for decades.

All of Oklahoma's incumbent House members face opposition in the Nov. 4 general election, but they will be heavily favored to be returned to Washington.

So will Inhofe, 73, who is seeking re-election to a third six-year term. Rice, 35, says he will have enough money to finance a strong challenge to Inhofe.

All of Oklahoma's U.S. senators and representatives are Republicans except Boren. So far anti-Washington sentiment that has cost some Republicans their positions around the country has not developed in the polls in Oklahoma, where the GOP has held a congressional majority over a decade.

The Democratic presidential nominee has not won in Oklahoma since 1964.

Key state Senate races will determine replacements for a pair of Republican term-limited senators — Kathleen Wilcoxson of Oklahoma City and James Williamson of Tulsa. Five-way GOP primaries have been waged in each of the two districts and runoffs are expected.

In southeast Oklahoma, Rep. Jerry Ellis, D-Valliant, is running for the Senate post Sen. Jeff Rabon, D-Hugo, is vacating because of term limits.

In Tulsa, a Republican primary will determine the opponent for Democratic incumbent Nancy Riley in a key Senate race for November.

Six Democrats are term-limited in the House, compared to only one Republican. But Democrats see some openings in several areas where Republicans are giving up their House seats. The departing Republicans include former Speaker Lance Cargill of Harrah and Greg Piatt of Ardmore, majority floor leader.

Rep. Randy Terrill, R-Moore, author of a sweeping anti-illegal immigration law, is among the incumbents facing opposition in the primary.

Polls will open at 7 a.m. and close at 7 p.m. on Tuesday in the state's 77 counties.