History

One of the most important things to understand about political violence is that the state (in this case, the US law enforcement) have a monopoly on legitimate violence. We just saw it today: the SS can legally kill the assassin with no problem, and of course that makes sense. But the point is that political violence against the state, as opposed to fringe groups like neo-Nazis, is hugely asymmetrical. The state doesn't face repression when they commit violence, for obvious reasons.

So political violence against the state (such as its electoral system and the candidates) is foolish and ineffective. An escalation, yes! It's an ineffective strategy, as we saw back around the late 1800s and early 1900s.