There is evidence, some quite strong, some rather specious, and all of it circumstantial, that John F. Kennedy had ties to the mafia, either personally or through his father. The theory is that the mafia, which then, as now, had strong influence in certain major labor unions, influenced the outcome of elections and prevented strikes in order to secure Kennedy his election wins (both as a Senator and as President), in return for presidential favors (either implied or explicit).

Also, if your definition of corruption extends to nepotism, then many presidents are extremely guilty there. Abraham Lincoln, for example, personally interceded to ensure his son Robert would not be drafted into the army, and when Robert volunteered, Lincoln got him a job on Ulysses Grant's senior staff rather than put him into the general pool of officers. It should be said that Lincoln did this at the behest of his wife, but either way, he clearly used his powers to create a standard for his son that differed from the standard of other Americans' sons at the time.

Can we stick to corruption guys? This is normally defined as having or showing a willingness to act dishonestly in return for money or personal gain. By this definition, neither Nixon nor Clinton were accused of corruption. JFK has been accused.

There is some strong speculation that the Harding administration was also involved in corruption, cronyism, and many scandals.

Its appears most came from his cabinet and it is unclear how much involvement he had.

His administration was coming under investigation at his death. Some speculate he could have been poisoned.

After his death his wife took considerable actions to make sure that alot of his stuff could not be accessed as well. I dont remember the exact words, but she was to have said something along the lines of, rest now they can no longer bother you.

Im sure there is another historian in here that can give more detail, mine is a little sketchy going by memory, but I do recall it was a very controversial administration.

Would discussing Bill Clinton violate the 20 year rule?