Senate candidates are expected to submit 15,000 valid signatures to get on the ballot. Democrats claim that over half of Roger’s 30,000 signatures may be illegitimate, with lawyers working for the party claiming to have found “patterns that indicate the presence of potential forgery and other fraudulent signature gathering tactics.”

Rogers, considered a frontrunner for the Republican nomination, was endorsed by former President Donald Trump in March. Primary elections will be held in August.

The Michigan Board of State Canvassers received the request for a probe late Thursday. The same concerned parties last week asked the board to look into the petitions of other GOP Senate candidates, too, among them former U.S. Reps Justin Amash and Peter Meijer (Meijer dropped out last month).