The single event that most tarnished Ford's presidency was his decision to pardon Nixon. He also, however, presided over the worst US economy since the Great Depression.
#4 Andrew Jackson attacked and captured Spanish forts, claiming Florida for the U.S. Monroe signed a treaty with the Spanish which gave Florida to the U.S.
Answer: Checks and balances.
Explanation: The whole point of establishing a system of checks and balances was to prevent one of the branches of government from getting too powerful. In order to prevent this, each branch of government has the power to stop another branch of government in the event that they are abusing their powers. In the executive branch (the president), this includes the ability to veto bills. In the judicial branch (Supreme Court), this includes the power to declare an action unconstitutional. And in the legislative branch (Congress/Senate), they have the power of impeachment.