There is way too much corruption and bribery in politics. One of the greatest causes is that politicians are bought by private interests, and therefore represent those interests, instead of the public interest.
Eliminating private funding will get rid of the favor system currently in place, as it will no longer benefit those seeking election. Create a fund that allots a specific amount of money available to each candidate, depending on the level of government. A federal office would get more funding than a state, who would get more than local offices. This would reflect the need of higher positions needing to reach more people. This would also have the added effect of leveling the playing field, so that the person with the most support can win an election, instead of the person who can buy the election.
Short of anything that causes Citizens United to be relitigated, there isn’t much we can do about PACs, other than changing the FEC reporting, so that we know where every dollar going to that PAC is coming from. It would still eliminate personal contributions (favors owed). Penalties for campaigns colluding with PACs should be immediate removal from position, and lifetime ban from holding any public office.