I'm not sure our perceptions of corruption agree with each other. Legally, an act of corruption would be paying a politician money to vote for legislation they otherwise wouldn't. But if a guy votes in patterns favorable to a specific industry, there's no effective barrier to him landing a cushy job in that industry later simply because he is admired and respected. If he puts it around he is interested in such a position, the big social circles in D.C. will introduce him to the right people.
For me, anything that isn't fanatical devotion to the ideals of public service is corruption. The only future for an ex-politician is the monastery. They can't be allowed any private gain from their political career because even the opportunities of that come with being an ex-public servant will have a corrupting influence on their ability as lawmakers.