Polls: Open from 7 a.m. until 8 p.m. EDT in most of the state, and from 7 a.m. until 8 p.m. CDT in a handful of counties in the western Upper Peninsula.
Voting: Cannot split tickets in the primary; votes must be confined to a single party column for partisan races. Voters will also be asked to decide millage issues and fill judge seats.
Rules: Must show a photo ID of some kind to vote (it doesn't have to be a driver's license). If voters don't have a photo ID with them, they can sign an affidavit and vote anyway.
Turnout: Secretary of State Terri Lynn Land expects voter turnout to be about 23 percent, or about 1.7 million voters.
Races to watch: Five Republicans are running for the GOP nomination: Oakland County Sheriff Mike Bouchard, Attorney General Mike Cox, state Sen. Tom George, U.S. Rep. Pete Hoekstra and Ann Arbor businessman Rick Snyder. On the Democratic side, House Speaker Andy Dillon is battling Lansing Mayor Virg Bernero for the nomination. The primary winners face off in the general election in November. Gov. Jennifer Granholm is term limited out of office after two terms.
Also on ballots
Sources: Michigan Department of State, AP and Detroit News research.