O'Connor and Balderson exchanged leads as the votes rolled in, with the Republican ahead by about 700 votes with 95 percent of precincts counted in the fight for a U.S. House of Representative seat.
Mike Flynn, a hospital unit coordinator from suburban New Albany northeast of Columbus, voted for Balderson as a show of support for Tiberi.
But the GOP candidate in the race, Troy Balderson, is a Trump supporter who recently welcomed President Trump at a town rally this weekend.
In Kansas, sitting Governor Jeff Colyer was locked in a close battle for the Republican gubernatorial nomination against immigration hardliner Kris Kobach, who received Trump's endorsement on Monday.
Democrats, meanwhile, have been attacking Balderson by casting his support of tax cuts as threats to Social Security and Medicare.
Cory Bliss, executive director of the Congressional Leadership Fund, a Republican-aligned SuperPAC, said: "While we won tonight, this remains a very tough political environment and moving forward, we can not expect to win tough races when our candidate is being outraised".
One of the primary season's true sideshows ended with a lopsided win - Rep. Ron Estes (R-Kan.), who won a 2017 special election in Kansas's 4th Congressional District, has defeated Ron M. Estes, who did not.
Should the polarizing Kobach win the primary, some Republican operatives fear he could lose the governor's seat to Democrats this fall. The race could become further disrupted if Kansas City-area businessman Greg Orman makes it onto the November ballot.
9-Year-Old NC Boy Selling Lemonade Robbed at Gunpoint, Deputies Say
John's Forest development off Weddington Road, and a teenager approached the boy around 3 p.m., the sheriff's office said. Officers believe the suspect "left a bicycle and walked from there to the lemonade stand before the robbery".
Trump made his preference clear for Kobach.
O'Connor dominated Balderson on the local airwaves. Strong on Crime, Border & Military. His campaign spent $2.25 million on advertising compared to Balderson's $507,000, according to campaign tallies of ad spending. Bernie Sanders and NY congressional nominee Alexandria Ocasio-Cortez, who catapulted to fame when she defeated the No. 4 House Democrat in a June primary.
In Kansas' 3rd District, Bernie Sanders-backed labor lawyer Brent Welder is running in a six-way primary to take on Yoder.
Also in the race: Native American attorney Sharice Davids and former school teacher Tom Niermann.
"A Republican loss well might tell us more". The field included Fayrouz Saad, who would be the first Muslim woman in Congress.
The 12th district, split between suburban Columbus, Ohio, and rural areas, has been represented by a Republican since the early 1980s.
Missouri Attorney General Josh Hawley is expected to take on McCaskill, and in MI, military veteran and business executive John James is vying for the chance to knock off Stabenow.
The night before the rally, Trump took to Twitter to attack LeBron James, calling the National Basketball Association star dumb just days after James, an OH native, poured tens of millions of his own dollars into the opening of an innovative public school in Akron.