On top of that, if trump would have been killed, there is technically nothing stopping the US from postponing elections, coming up with an intermediate solution to have a functioning government without a D. president (like, no appointing of judges and such) and then have an election next year when the Republicans had enough time to find a new candidate.
If trump pushes through the things he said he’d do and what his supporters are supporting like project 2025, there’s a real chance that there are no actually democratic elections in 2028. And this is ignoring the fact that gerrymandering and the electoral college are already questionable and regularly abused by or benefit Republicans the most.