I think people are missing that Michigan has open primaries and no party registration, and at least in my district you didn’t even have to tell the poll worker if you wanted a Democrat or Republican ballot. The ballot had both the Democrat and Republican candidates on it, and you were only allowed to fill in one column (or it spoiled your ballot).

Most of the republican candidates were running unopposed or effectively so, so there wasn’t much reason for anyone to vote in the Republican column. The Democratic primary polls were of "Democrats," though, which probably explains most of the discrepancy between the polling and the results.