Congress hasn't heard from anyone on the July 25th phone call between Presidents Trump and Zelensky - until now. Lt. Col. Alexander Vindman testifies to investigators on the Hill as a GOP member attacks the Purple Heart recipient's patriotism. Meanwhile, Nancy Pelosi finally decides to hold a vote formalizing the impeachment inquiry. What are the political implications? CNN political director David Chalian examines the latest developments with CNN reporter/producer Marshall Cohen. Plus, impeachment expert Ross Garber speculates on President Trump's potential impeachment trial defense.