Bernie Sanders' message about corruption is a significant part of his campaign. He speaks forcefully about a system in which legislation and political favors are essentially bought by donations from large donors. He does not call out any individuals as such. There's a good reason for that: the kind of corruption Bernie is talking about isn't bribery. It's a systemic corruption that relies on the concept of "reciprocity": a person's sense of obligation or indebtedness to a person who gives him or her a gift. An individual doesn't have to "be corrupt" in order to facilitate and propagate systemic corruption if it exists.

This isn't as well studied a phenomenon as some others, but there are studies about it. NPR had a recent story that indicated it's at work in our health care system. Physicians prescription habits are closely correlated with the funding they receive from pharmaceutical companies. The same phenomenon reaches an "extreme" point in politics when bribery or campaign funding violations occur.

In our political system, corruption does exist and it is systemic. Studies show that wealthy, connected individuals and lobbyists (funded by the wealthy) have a near monopoly on our politicians' attention. This isn't because they're the only ones trying, it's because they're the ones who control the funding and media for politicians. They also influence strongly political parties' support, and therefore have a hand even in selecting candidates to run for office. This kind of corruption isn't always explicit bribery or influence peddling. It's tacit, implicit; an "unwritten rule" that everybody who's anybody just knows and absorbs.

So when Bernie brings this issue up in debates or at rallies, he's not talking about his opponent as an individual who is corrupt, but about a system in which the kinds of political funding she takes has a corrupting influence. It's a real problem, and it's self perpetuating. There are ways to reduce its impact on our political process. One is to have a candidate who inspires lots of small donations, as Bernie has. However it's too easy to get cash the corrupting way (on purpose), so this isn't sustainable. Changing this systemic corruption will require a radical change to the way our elections are conducted: they must be free, and entirely publicly run and funded.