The open impeachment hearings continued Tuesday with testimony from top Ukraine expert Lt. Col. Alexander Vindman, Vice President Pence adviser Jennifer Williams, National Security Council official Tim Morrison, and former special Ukraine envoy Kurt Volker.

Vindman used his time to emphasize his alarm at President Donald Trump’s summer phone call with Ukrainian President Volodymyr Zelensky and defended his record of service to the United States. In the afternoon, Volker gave testimony that revised his earlier closed-door deposition, including a significant change from his earlier claim that he had no knowledge of Trump making inappropriate demands of a foreign power.

To discuss, Jim Braude was joined by Heather Cox Richardson, a historian at Boston College, and Carol Saivetz, senior advisor at MIT’s Security Studies Program.