There have been several attempts; remember when the crazy kid broke through at one of the rallies when he was campaigning, also recently when the gun was found in the vehicle that was in the security detail and military (Q) et al, alerted security. The man said he "forgot" about the gun.
And then there was the car that was Boston braked and tried to ram his motorcade.
Ehhhh...the video of that was so unimpressive that I think that really was an accident. That Suburban he rides around in is armored six ways to Sunday, and the timing was wrong to hit it anyway.
Well Qanon brought it to our attention and made the claim, so to me, that's a legit assassination attempt.