O'Donnell has sat on the Cuyhoga County Court of Common Please since 2002. Justice French was appointed to the Supreme Court at the end of 2012 by Gov. John Kasich, and before that served on the court of appeals.
O'Donnell is endorsed by the Ohio Democratic Party and says he'd bring a new perspective to the court -- but won't be campaigning as a party standard-bearer.
"I am not telling you that I am conservative or liberal or moderate," O'Donnell said. "I am telling you, as I did in my presentation today, that I have a broad array of experiences that have rendered me I think capable of good service on the court."
O'Donnell says his experience trying felony criminal cases and major commercial lawsuits qualifies him for the court.
Currently there's just one Democrat on the seven-member Supreme Court. A win for O'Donnell would make it two -- and there could be a third. Republican Justice Sharon Kennedy is also up for re-election, and will likely face a Democratic challenge.