Do they have our political party registration? Who would want to hand that over to Mr. Retribution?

In Michigan, you don't declare a party affiliation when you register. For a vote suppression program, you could select the people in Dem leaning districts for scrutiny, but, as others have said, the government already has your address, so they can figure out the affiliation of the people most in your area vote for. Maybe they have more elaborate data sifting in mind, by age, race, gender? I just looked at my Michigan driver's license. It shows DOB, gender, and eye color, but not race. Maybe sift by name, looking for non-WASP names, then correlate the non-WASP names with districts represented by "the enemy"?

Why is the DOJ keeping their intentions secret, even from the state government officials, they are demanding the information from, if their intentions are not nefarious?

Steve