As President Trump’s second-in-command, Vice President Mike Pence could become a key figure in the impeachment inquiry. The first staffer from his office, special advisor Jennifer Williams, testified before Congress on Thursday. Pence has spoken with the Ukranian president Volodymyr Zelensky over the phone multiple times and met with him in early September. But Pence continues to avoid specific questions about his knowledge of events surrounding the hold up of aid to Ukraine. NBC Political Reporter Vaughn Hillyard walks through what we know about Pence's involvement in the events at the center of the impeachment inquiry.

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For a transcript, please visit https://www.nbcnews.com/articletwo.