Who are some of the most corrupt American Politicians of all time?

That is a subject for historians to debate, and many articles have been written about it. Some Republican opponents of President Obama say he is the most corrupt, but the facts do not support such a claim. More likely, it would be someone like Warren G. Harding or Richard Nixon. I enclose a link to an article from the magazine U.S. News & World Report, which gave their opinion on some of the worst presidents.