Attorney and University of Michigan regent Mark Bernstein won't run for governor in 2018 and is endorsing Gretchen Whitmer.
The Democrat announced his decision Tuesday.
He says on Twitter that a "divisive and expensive" primary would only distract Democrats from winning the general election. Republican Gov. Rick Snyder is barred from seeking a third term.
Bernstein is the president of his family's prominent Detroit-area personal-injury law firm. His brother is on the Michigan Supreme Court.
Bernstein says a "strong motivating force" in his deliberations was his desire to be a candidate with "decency and dignity."
Six Democrats have filed paperwork to run. Whitmer, a former Senate minority leader, is considered a top contender. Others running include former Detroit health director Abdul El-Sayed, ex-Xerox executive Bill Cobbs and entrepreneur Shri Thanedar.