I have to admit being one of those people very upset by the Supreme Court rulings on campaign finance over the past years. The majority opinion has been that without a quid pro quo agreement, money does not create a corrupting influence. But anyone familiar with behavioral science knows that this could not be further from the truth. When someone does you a favor, even with no discussion whatsoever of any reciprocation, you develop at least an unconscious if not an overt urge to reciprocate. And when it is unconscious, the influence can be even more dangerous because you can’t inhibit what you don’t even know about.
So a lobbying group or donor of some kind gives a large sum of money to a political campaign. They don’t ask for anything in return except for the politician to listen for a few minutes to their case. The politician will be influenced nonetheless. Even just being predisposed to be open to the argument can make it more convincing that the other side’s argument that was not accompanied by a donation.
The lobbying group may even say explicitly that they don’t want any favors in return. This can often lead to an even stronger reciprocation urge. The more strongly you insist you don’t want a favor in return, the stronger the urge to give you one. Yes, it happens. But the Supreme Court doesn’t seem to get this.