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COLUMBUS, Ohio-- A nonprofit behind $1 million in independent advertising against U.S. Sen. Sherrod Brown had business links to a one-time aide to Brown's opponent.

Its attorney says The Government Integrity Fund airing the ads is led by Statehouse lobbyist Thomas Norris.

Documents show Norris shared office space and some lobbying clients with Joel Riter, a former political operative to Republican Senate challenger Josh Mandel.

Any coordination between Norris' firm, Cap Square, and Mandel's campaign is prohibited under federal election law.

Riter said Friday he had no involvement with the nonprofit or the advertisements.

The nonprofit's attorney, William Todd, said Riter was a contractor who did no coordinating.

Todd said the nonprofit observed the Brown-Mandel campaign in putting together ads. Online news organization Pro Publica first reported the business tie.