With 90.84 percent of precincts reporting, Sprague was ahead by a margin of 14.76 percent, according to the Ohio Secretary of State's website. He declared victory.
"I'm overwhelmed with gratitude for the Republicans who put their trust and confidence in me to be our Party's candidate for Treasurer in November," Sprague said in a emailed statement. "I am fully committed to continuing to run a campaign that people can be proud to support and to serving as Treasurer of State with the integrity that Ohioans deserve."
Sprague, a state representative from Findlay, will face Democrat Rob Richardson in the general election.
Sprague entered the race more than a year ago and secured the nomination with the muscle of money and strong party support. He raised hundreds of thousands of dollars and earned the endorsement of the Ohio Republican Party. Poll numbers sampled between April 24 and May 2 showed Sprague with a slight lead, though the majority of voters were undecided.
O'Brien, a former Ashtabula County auditor, entered the race in December, and raised less than $1,000. But she was more of a threat than her campaign finance numbers indicate: This was the third time her name appeared on a statewide ballot and in a down-ballot race, name ID matters.
Plus, O'Brien won this contest before. She secured the GOP nomination for the treasurer's race in 2006, before she was defeated by now Democratic gubernatorial candidate Richard Cordray in the general election. She also ran for secretary of state in 2010.
O'Brien did not return a call for comment.
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