Schuette, whose national profile has grown during his investigation of Flint's crisis with lead-contaminated drinking water, made the announcement at his annual barbecue for supporters in his hometown of Midland.
The 63-year-old former congressman, state senator, state Cabinet official and appellate judge has cast himself as a "voice for victims" as the state's top law enforcement officer. His probe into Flint's public health emergency led to criminal charges against 15 current and former government officials, including many in the administration of second-term Republican Gov. Rick Snyder, who cannot run again due to term limits.
Democrats plan to keep the water crisis in the predominantly African-American city on voters' minds, accusing Schuette of initially dragging his feet on investigating it and mishandling some parts of the scandal.
During his campaign-opening speech, Schuette avoided the subject of Flint.
"My one goal, my singular ambition is to make Michigan a growth state, a paycheck state, a jobs state," Schuette told hundreds of supporters at the county fairgrounds. "To achieve this, we must have a jobs governor."
He called for lowering the state income tax from 4.25 percent to 3.9 percent and warned against electing a Democrat as governor, citing the "lost decade" under former two-term Gov. Jennifer Granholm when the auto state shed hundreds of thousands of jobs.
Schuette said Michigan has rebounded under GOP leadership but has only begun to fulfill its potential and families "have to start winning again." He said "Democrat elites' answer to lost jobs and lost income is more government and more dependency."
Schuette can use the $1.5 million in his attorney general campaign account for his 2018 gubernatorial bid. Dr. Jim Hines and state Sen. Patrick Colbeck are the other main GOP candidates running, though Lt. Gov. Brian Calley — a Snyder ally — is weighing a bid. The conservative Schuette and more moderate Snyder have had a testy relationship.
Democrats desperately want to retake the governorship, and Michigan has been a top target nationally, even before Donald Trump's surprise win over Hillary Clinton in the state last year. Their diverse field includes presumed front-runner Gretchen Whitmer, a former legislative leader; ex-Detroit health director Abdul El-Sayed; Shri Thanedar, an immigrant entrepreneur from India; and Bill Cobbs, a former Xerox executive.
The Democratic Governor's Association said Schuette "is only on duty for special interests and political cronies," and accused him of wasting public funds on "political" lawsuits and opposing the interests of working-class people. Critics also blasted Schuette for defending the state's gay marriage ban and challenging former President Barack Obama's health care law and pollution regulations.
Republicans' hold on the White House and Congress could be a bonus in 2018 for Democrats, who will have been out of power at the state level for eight years. The last time a gubernatorial candidate won Michigan and was from the same party as the president was 1990.
Schuette acknowledged the difficulty of winning the governorship given the cyclical nature of politics and voters' desire for change but said the state cannot return to Democratic control. He cited his record defending the state's affirmative action ban in college admissions, fighting to test abandoned sexual assault evidence kits and combatting human trafficking.
"2018 won't be easy," he told reporters. "You've got to have your strongest, toughest Jedi Knight. I'm like Obi-Wan Kenobi, I'm our only hope. But the point here is I'm not in the established group in Lansing. I have my own (independently elected) office, and I have an independent record of accomplishment."