Why presidential stonewalling of oversight is threat to democracy

It is a basic principle of the Constitution that the president is not above the law and is checked in his exercise of executive powers in a variety of ways, including civil lawsuits, criminal investigations that may lead to impeachment, and oversight by the Congress. If Trump can get away with ignoring subpoenas from another branch of government, then we have lost an essential check on the power of the presidency for the future. 

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