To answer your question... it does not take a rocket scientist to judge who is honest and who is crooked. It does, however, take eternal vigilance (read that NAG the H*LL out of your congresscritter) to keep them honest.
Example: In the thread about Senators voting for or against the UN gun treaty... I wrote both of my senators and told them:
Either I see the record showing you voted AGAINST this, or I do everything in my power to see you retired at or before the next election... no options.