Sure, there was the attempted assassination of Reagan and the fears for Obama as the first black President, but in those cases it was a lone nutter rather than a conspiracy.
How long can Trump crash the market before an angry billionaire decides to take him out? The remaining Koch brother is already pouring money into legal challenges against Trump…
A better question would be is it even possible to do in the first place?
It’s possible. The Swiss Cheese Service demonstrates that last year.