I actually know this one, because my dad is a poll worker (I'm too much of a partisan to be one). It's run by state election boards, which have, for the most part, evaded capture by the administration. Additionally, elections are a massive undertaking that requires lots of advance work.

Places are going to be preparing for the midterms soon, and the administration, outside of executive orders, hasn't done much to actually take control, likely because the concept of advance planning is unfamiliar to them.

If he doesn't start seizing control (which he'll have to do through governors and state legislatures) soon, things will be locked in, and he won't be able to do much.

Trump thinks he does. I’m sure we’ll see if his Supreme Court agrees soon.