O'Neill graduated from Cleveland Heights High School in 1965 and Ohio University in 1969, at which point he joined the U.S. Army.

[1] In a 2004 special election to finish the term of an Ohio Supreme Court justice who resigned, O'Neill lost to Terrence O'Donnell by 21%.

O'Neill stated during his campaign his desire to expand the Greater Cleveland Rapid Transit rail system.

[14] O'Neill ran on a budget of just $4000 from his personal funds, a campaign he called "no money from nobody" and that was highlighted in a YouTube video with his twin sons.

During his announcement, he laid out a platform of minimum wage increases, tax incentives for solar power, mental health care expansion and marijuana legalization in Ohio.

[15] Less than a week later he announced that he will recuse himself from new Supreme Court cases and will resign by the February 7, filing deadline due to potential ethical conflicts.

He referred to those calling for Franken to resign as "dogs of war" and decried a "national feeding frenzy" against age-old sexual indiscretions.

[18] Multiple state officials, including Ohio Chief Justice Maureen O'Connor,[19] former state representative and fellow gubernatorial candidate Connie Pillich,[20] Dayton mayor and fellow gubernatorial candidate Nan Whaley,[18] and Lieutenant Governor Mary Taylor,[21] criticized O'Neill's comments, with Pillich and Whaley calling for him to resign from his position as justice.