Updated

Michigan's attorney general has charged four of former U.S. Rep. Thaddeus McCotter's campaign staffers in an investigation into fake and duplicate signatures on nominating petitions.

Attorney General Bill Schuette announced charges Thursday ranging from forgery and conspiracy to falsely signing election documents.

McCotter isn't charged. Schuette says there's no direct evidence of McCotter's involvement but he says the congressman was "asleep at the switch." Schuette wouldn't rule out more charges in the future.

The petition scandal knocked the congressman off the ballot and led to his resignation July 6.

The 46-year-old McCotter's failure to submit the needed signatures paved the way for tea party-backed Kerry Bentivolio to win the district's GOP nomination in Tuesday's primary. He faces Democratic Dr. Syed Taj in the Nov. 6 election.