In Ohio 17 year olds who will be 18 by the next general election are allowed to vote for candidates only (not on issues). This makes sense, considering that they will be able to vote for the candidates who win the primary, so they should have a voice in choosing candidates in the primary.
In Michigan you can register to vote in the primary at 17 but only if you’re going to be 18 by primary day.
“This makes sense[....]”
Allowing a minor to vote in an official government election makes no sense at all, not even in a primary, when you note how the minor is not emancipated and has no legal authority to make contracts or be responsible for the person’s own acts and misdeeds. This amounts to the fundamentally illegal and unconstitutional granting of unemancipated authority with no responsibility.