What people forget is that it's damn near impossible to pull off a 'conspiracy theory' type scheme. Not only do you have to ensure that every single person involved (and there would have to be quite a few) won't talk, you have to ensure that every person who you approached to be part of the plan and who turned you down ALSO won't talk / share evidence with the media and/or police.
People are incapable of keeping quiet about office drama or who is fucking who in their friend group, let alone a criminal conspiracy to assassinate a political candidate.
Sure, some nutjob will say he was approached, but he'll have no evidence because it didn't actually happen.
This applies to all conspiracies, left wing and right wing. So to all the 'false flaggers' out there - sorry, but no.