Descent into fascism is a process not an end state.
Examples:
using government regulatory authorities to silence speech the powerful don't like.
Plain clothes security forces rounding up people without due process.
The Supreme Court using the shadow docket to push through blatantly unconstitutional decisions in favor of the current administration
The rule of law being repeatedly ignored with no consequences
I'd say that for the midterms to change anything the dems would have to have crushing victories in both the House and the Senate. I'm not sure, but I think in the Senate that's utterly impossible, even with the assumption of entirely free and fair elections. Also that assumption is becoming less and less guaranteed. Additionally, even if the dems win overwhelmingly, if they keep behaving in the same way they did during the Biden mandate, they will, at best, be an hiatus.
I don't think Trump is necessary anymore, at this point the GOP seems entirely captured by its far right faction. Still, what happens to the GOP with a dead Trump is a bit of an open question. I sometimes have conversations with a colleague of mine who thinks Vance would be worse than Trump. I think he'd be a lame duck.