It isn't...

American politicians are corrupt. However, not everything they do is corrupt too. Corrupt isn't voting against your consituency because you feel they'd be better served. Corrupt isn't appropriating money back to your district through riders in legislative bills. Corrupt isn't cheating on your wife even when you campaign on family values. Corrupt IS accepting cash contributions or corporate compensation to write in legislation that protects or contributes to the ability of multinational corporations to hide or circumvent through the federal business laws. This help can vary from amending zoning laws upto tax evasion. Everything else is just business as usual since 1776.