Well assassination of a candidate duration an election has some precedent. But it doesn’t happen often for good reason. If you assassinate a political figure you make them essentially a martyr for their campaign or ideals which stops people thinking rationally and doubling down on their emotional reaction to the assassinee’s party or general ideology. People put aside differences to “carry the torch”.

Honestly killing Trump and pining it on leftist bogeymen would be a move I could see some Republicans doing. They have basically primed their base to accept any shlock they want to pass as news and if they go full authoritarian and get enough support on board to basically ignore democratic checks and balances…