What can we do to make our politicians more honest?

I asked a question somewhat recently about whether or not we essentially encourage politicians to be slimy. Although virtually no one agreed with me, I still feel like it is true.

Whether or not we encourage that kind of behavior, we certainly accept it. Most of us expect politicians to be dishonest. Then, when they prove to be dishonest, little or nothing is done about it.

What steps could be taken to reverse this trend? Do politicians have to be dishonest, or is this just something that has grown out of hand?