Donald Trump in a second term would likely install loyalists in key positions in the Pentagon, State Department and CIA whose primary allegiance would be to him, allowing him more freedom than in his first presidency to enact isolationist policies and whims.
If he is reelected it will be a Brexit-like self imposed wound on the US that I fear we will never recover from. If we lose Ukraine and weaken NATO, America loses. If he installs cronies willing to break the law for the supreme dictator, America loses. 2024 elections are existential.
I hate to say it, but until we can revamp our education system, educate the "low information voters", and eventually vote properly with the idea of progressing our nation to help all, every election for the foreseeable future will be existential.
But yes, this one, I agree with you, is really the big one.
Part of the plan is to cancel the election security agency. so I'm not sure there will eventually be other elections where you do all of these things if this one is lost.