The impeachment inquiry has largely been a showdown between co-equal branches of government, pitting the White House against Congress. Now the courts are wading into the drama. Former deputy national security adviser Charles Kupperman defied a Congressional subpoena and asked a judge to decide if he should testify in the inquiry. Might this be a new tactic in Trump's attempt to stymie his investigators? CNN political director David Chalian dives into the latest impeachment headlines with the publisher of CNN's impeachment watch tracker, Zach Wolf, and CNN legal analyst Michael Zeldin.

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