The Michigan Secretary of State's office says people who want to be poll watchers or challengers have to abide by the rules.
Spokesperson Tracy Wimmer says a poll watcher is exactly that: just someone who heads over to a polling place and observes what's going on. They're basically just a fly on the wall, and can't interfere with voting or the workers.
There are also rules for people challenging someone's right to vote.
"Challengers are not allowed to speak directly to voters," says Wimmer. "They must make any challenges to the election inspectors, the poll workers present. And they also cannot make a challenge based on just an impression of the voter. They can't look at the color of someone's skin, they can't say, 'I heard this person speaking a different language.'"
For that reason, people who challenge a voter's right to cast a ballot have generally identified someone in advance whom they believe is ineligible but is planning to vote.
Wimmer says voters who are approached directly by someone telling them they can't vote should immediately tell the poll workers.