I'm having a hard time differentiating between what Governor Blagowhatsit of Illinois is accused of doing and what politicians do all the time. Is it unusual for a governor to expect some kind of favor in return for naming your preferred candidate to the Senate? No, but you're not supposed to say it out loud.
There are lots of circumstances where folks are supposed to pretend that they are disinterested when they clearly are very interested or to act is if they are not doing what they are clearly doing. Take churches, for instance. They do "outreach" or "evangelism", not marketing. They are, in many respects, no different from any other enterprise, but it would be offensive to acknowledge this by using ordinary business language. You have to conceal what everyone already knows.
In politics, everyone knows that you give money to a politician's campaign in order to influence how he will vote or, at best, because you expect that he will vote your way. It's not bribery as long as you don't say out loud that it's specifically in consideration of political acts even though everyone knows that it's in consideration of political acts. Nobody believes for an instant that the NRA or any special interest group gives money to candidates simply because they reckon they are good for America. They are buying the politician. He has probably announced in advance whom he would like to be sold to in order to facilitate getting payments fast, but he's still for sale.