A day-and-night bombardment of negative television ads has turned many voters off from the especially nasty campaign to replace Sen. Don Nickles (search), an Oklahoma Republican retiring after 24 years.

"There's smearism on both sides of the fence, and we're sick of it," retired nurse Brenda Clark yelled as she left a town hall meeting for Republican Tom Coburn (search) in this college town.

Polls show Coburn, a former congressman, about even with Democratic Rep. Brad Carson (search) in one of fewer than 10 contests that could determine control of the Senate, where the GOP now holds a majority of 51-48 with one independent.

The negative ads include allegations that Coburn, an obstetrician, sterilized a woman without her consent and gave a fraudulent bill to Medicaid for the procedure. Coburn's ads claim Carson is a liberal pretending to be a conservative to appeal to voters.

Oklahoma hasn't backed a Democratic presidential candidate since Lyndon Johnson (search) and is expected to support President Bush in this election. The retiring Nickles, chairman of the Senate Budget Committee, is among the most fiscally conservative members of the Senate.

Coburn is reaching out to evangelical Christians as the race enters the home stretch.

The election, he told a town hall meeting here, will determine "whether the right people are going to be in control of the U.S. Senate or whether the wrong people will be in charge."

"It's a race," his Democratic opponent said in a western Oklahoma campaign stop, "that I think will be talked about for generations to come."

Carson, a 37-year-old lawyer, wears cowboy boots and jeans and drives the campaign trail in a beat-up pickup truck he's owned for a decade. He calls himself a member of the "Oklahoma Party" first and touts his conservative credentials, ranging from his vote against same-sex marriages to his support of President Bush's tax cuts.

"Our challenge is to point out that when Tom Coburn calls me a liberal, it says more about him than about me," Carson said. "Everyone is more liberal in comparison to Tom Coburn."

"What is a conservative Democrat in Washington is a liberal in Oklahoma every time," Coburn said during a televised debate.

Carson replaced Coburn in the House after the Muskogee doctor kept his campaign promise to serve no more than three terms.

The state's Republican establishment already had rallied behind a more moderate candidate, former Oklahoma City mayor Kirk Humphreys, when Coburn announced his intention to seek election. Coburn won the primary with 61 percent of the vote.

Coburn, a strident abortion foe whose specialty is delivering babies, sees the race as a battle for the next generation's future. In an Associated Press interview, he said he favored the death penalty for abortionists.

He has hammered on the "evil" of excessive government spending and blamed career politicians for harming Social Security and Medicare. Incumbents, he says, ignore difficult issues and exacerbate the deficit by sponsoring programs to get re-elected.

Carson accuses the Republican of voting against Oklahoma's interests and doing nothing when he was in Congress to bring money or jobs to the 2nd District.

"We have never sent anybody to Washington who made not doing anything for us his platform," Carson told voters in western Oklahoma counties that suffer from an exodus of people and jobs.

Known as an outspoken maverick in Congress, Coburn's blunt comments while campaigning have stirred controversy.

He drew fire for saying "a bunch of crapheads in Oklahoma City" had stymied economic development. After he referred to "rampant lesbianism" in southeast Oklahoma schools, the Tulsa World suggested in an editorial that the nation's threat code be raised to "Code Hot Pink."

Coburn also has had to defend against the sterilization allegations from a former patient who said Coburn did the procedure in 1990 without her permission.

The allegations, disputed by Coburn, were contained in a lawsuit that was dismissed after the woman failed to pursue it. He also disputes allegations by Democratic Attorney General Drew Edmondson, among others, that Coburn engaged in Medicaid fraud in the way the procedure was billed.

Coburn says the accusations are part of a Democratic smear campaign. He warns that Carson's election would mean that liberal Democrats like Ted Kennedy and Hillary Clinton would run the Senate.