Republican gubernatorial candidate Bill Schuette has submitted 26,000 voter signatures to qualify for the August primary, the same day Democratic rival Gretchen Whitmer secured another union endorsement.
Schuette, the state attorney general, is the third Republican to file petitions before April's deadline. He joins state Sen. Patrick Colbeck and Jim Hines, a Saginaw doctor.
Lt. Gov. Brian Calley is also running. Candidates need 15,000 valid signatures.
Schuette said Friday that collecting and submitting petitions within six months of announcing his candidacy is a show of organizational strength.
Whitmer, a former legislative leader, now has the backing of Teamsters Joint Council 43, which has 65,000 members.
International Brotherhood of Teamsters General President James P. Hoffa says Whitmer is "our strongest candidate to take back the governor's office and get things done."