LANSING, Mich. — Republican gubernatorial candidate Brian Calley on Tuesday submitted 25,000 nominating signatures to qualify for the ballot, saying he wants to continue Michigan’s economic turnaround with a positive campaign despite his allies airing negative TV ads against main rival Bill Schuette.

Calley, the lieutenant governor, declined to say the state attorney general is “shady” — as has been alleged by an independent political action committee backing Calley. He said he would leave it to super PACs backing himself and Schuette to argue back and forth, but “naturally these things happen” in the political system.

“As for me, I’m going to stay focused on building the best and strongest Michigan we can possibly have,” Calley said, only to tell reporters when pressed that there “clearly have been aspects of the attorney general’s campaign that have been very, very questionable.”

He pointed to Schuette’s alleged conflicts of interests in his investigation into Michigan State University’s handling of disgraced former sports doctor Larry Nassar, his “politicization” of the criminal probe related to Flint’s water crisis and his putting constituent relations representatives on the attorney general’s office payroll while they have also worked on behalf of his campaign.

Schuette — who has led the GOP field in early polling — has pushed back against such criticism, saying that Flint residents who were poisoned by lead in their water or who died in a Legionnaires’ disease outbreak deserve their day in court. He appointed a special assistant attorney general to handle the ongoing MSU investigation that has led to charges against the former dean of the College of Osteopathic Medicine.

Schuette campaign spokesman John Sellek accused Calley of trying to hide is record of raising taxes and questioned “why anyone would take (Calley’s) word at this point” after Bridge Magazine recently took Calley and the pro-Calley super PAC to task for inaccurate ads.

While turning in the petitions, Calley was joined by his wife — state Rep. Julie Calley — and their three children. He reiterated policy goals such as improving K-12 education, preparing workers for future in-demand jobs and eradicating the opioid addiction epidemic.

He is the fourth Republican gubernatorial candidate to file before the deadline next week along with Schuette, state Sen. Patrick Colbeck and Dr. Jim Hines. Two of the four main Democrats have filed so far. The primary election is in August.

To qualify, a gubernatorial candidate must gather at least 15,000 valid voter signatures from at least seven of the 14 congressional districts.

Also Tuesday — which is the deadline to file tax returns — Schuette highlighted his past signing of a pledge to not raise taxes, saying he is the first candidate in either party to do so as a gubernatorial candidate. One of his top campaign planks is an income tax cut, and a super PAC allied with Schuette continued to attack Calley for voting to raise business taxes when he was a legislator and for backing fuel tax and vehicle registration fee hikes as lieutenant governor.

Republican Gov. Rick Snyder cannot run for a third term because of term limits.

Follow David Eggert on Twitter at . His work can be found at