Washington (CNN) Former Trump campaign aide Sam Nunberg said in a CNN interview that he would refuse to appear before a federal grand jury after being subpoenaed in special counsel Robert Mueller's investigation into Russian interference in the 2016 US election.

So, who exactly is Sam Nunberg, beyond a former adviser to President Donald Trump's campaign team? Well, he's a man who Trump has hired, fired, rehired, refired and then sued for $10 million.

A history with Trump of being hired, fired and sued

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