You won't like the answer.

Bribery works for most people, but is often much more subtle than simple quid pro quo. Things like offering a child of bribee business deals, etc. Jack Abramoff has talked about this pretty openly since his conviction.

Now, when bribery doesn't work, it gets darker. Blackmail, extortion, threats against family members, and worse.

I'll leave it there for now, but in general most people in DC seem to just be thinking "I'm gonna get mine for me and my family, fuck everyone else."