The people need to hold them accountable and make sure politicians are properly investigated and pay their fines like Obama's campaign did or go to jail if the severity of the offense warrants it. Don't let them get away with walking all over the laws your elected officials set up to protect you.
If the candidate does it straight, the party or other contributors cheat for them.
I'm sure the cheating that the Obama campaign was caught at only scratched the surface of the total cheating that went on in his behalf, with or without his knowledge.
The system is devised so that they can cheat with impunity and only get caught once in a while. And like the crooks that backed Obama, just pay a fine. Hillary and her supporters have been caught numerous times. Nobody ever goes down. The Chinese that bought Bill just went back to China to avoid prosecution. Ad nauseum...