What to watch: Four Republicans and three Democrats are running for governor of Michigan. On the Republican side, the top contenders appear to be Attorney General Bill Schuette and Lt. Gov. Brian Calley. On the Democratic side, the candidates are former State Senator Gretchen Whitmer; Shri Thanedar, a businessman; and Abdul El-Sayed, a progressive former director of Detroit’s health department. Read more

Two businessmen are running in a Republican primary to challenge Senator Debbie Stabenow, a three-term Democratic incumbent. They are jockeying for the Trump vote, and Mr. Trump weighed in late last month, endorsing John James over Sandy Pensler. A poll conducted shortly before the endorsement showed an extremely close race, but Mr. Trump’s support could give Mr. James the edge.

Five House races are also expected to be competitive in November, especially the Republican-held Eighth and 11th Districts. In the Eighth District, two Democrats — Elissa Slotkin and Chris Smith — are vying to challenge Representative Mike Bishop. And in the 11th District, where Representative David Trott is retiring, there are crowded primary fields on both sides.

Finally, keep an eye on the 13th District, where John Conyers Jr. resigned last year because of sexual harassment accusations. It’s a safe Democratic seat, but the primary is hard-fought, with Mr. Conyers’s son and great-nephew both running.

— MAGGIE ASTOR

Read more about today’s most important races.