Not at all, no. The US government is and always was extremely nationalistic (not nationalist, not national socialist, those are different things) and by being that, there were and are groups that do whatever they need to do to achieve their goals (i.e. “not the goals of the opposite party”). Let it be assassination, bribery, or downright capitalism.

I would actually be extremely surprised if the republicans are not somehow involved in killing a democratic president. (I wouldn’t be surprised if it was the other way round, too.)