Key impeachment 'drug deal' witness willing to defy Trump

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Star witness John Bolton, Trump’s former National Security Advisor, is preparing to potentially testify against Trump in House Dems’ impeachment probe. Bolton is a key witness, with high ranking credentials, who reportedly had a devastating objection to the Ukraine plot in real time, calling it a ‘drug deal.’ Experts join Ari Melber to discuss breaking news developments and the latest in the impeachment probe.