I think everyone who is paying attention, without regard to their political leanings, has noticed a definite change in Trump's behavior. We can call it a decline, but it's apparent and quite sudden.
If we take Donald Trump as we know him, and lay a veneer of post traumatic stress syndrome disorder on top of it, the changes in his behavior make sense, at least in medical terms. It would be truly bizarre if getting shot at had no effect at all. I don't know what kind of personality disorder could allow a person to survive that experience and it not show an kind of symptoms.
I honestly mean this - I suspect the media paying more attention to Harris/Walz than him affected him more than the assassination attempt. The attempt was all about him so he's probably coping with that better than being cast aside. He is that broken and has been for years that's probably where his priorities lie.
All of Trump's pathologies have been chronicled for sometime and it's not really possible to say which stimulus makes him flinch more or less.
Without going into details, I've been living with a person who has severe PTSD for about 5 years and I've been able to observe the personality changes. Some are obvious and some are very subtle. I called it a "veneer of post traumatic stress syndrome" because that's what it is. A thin layer over every action and reaction. It's most apparent in reactions to stress and sudden disorder is very stressful. Trump started the race feeling he had a better than even chance at beating Biden. With no warning, Harris is his opponent and every single aspect of his future plans change. Don't forget he has a court date coming up, followed by many court dates yet to be determined. He has a lot on his mind and then someone tries to kill him, for no apparent reason.
The result is, a man with little empathy has even less empathy, and his narcissism becomes more self centered. One of the most common symptoms of PTSD is second guessing every decision. It's a natural reaction, like the person who gets hit by a car crossing the street. Their mind keeps going back to every step of the day, wondering if they had paused here, or walked faster there, would they have been somewhere else when the car went by. For a person like Trump, who has always believed his judgment is superior to all other people, that is a crippling handicap. Recovery is a very slow process and I don't think he has that much time.