House Intelligence Committee Chairman Adam Schiff, D-California, prepares to question witnesses Jennifer Williams, an aide to Vice President Mike Pence, and National Security Council aide Lt. Col. Alexander Vindman, on Capitol Hill in Washington on Tuesday during a public impeachment hearing of President Donald Trump's efforts to tie U.S. aid for Ukraine to investigations of his political opponents. Credit: J. Scott Applewhite | AP

The House Intelligence Committee will hear public testimony Tuesday afternoon from Ambassador Kurt Volker, the former U.S. special envoy to Ukraine and Timothy Morrison, special assistant to the president and senior director for Europe and Russia on the National Security Council. It the fourth public hearing as part of the ongoing Trump impeachment inquiry.

Volker has provided text messages to lawmakers that revealed an effort at the State Department to push Ukraine’s leader into opening an investigation of the gas company Burisma in return for a visit with Trump, according to The Associated Press. Volker stepped down as special envoy to Ukraine after the impeachment inquiry had begun.

Meanwhile, Morrison’s testimony ties Trump more closely to the central charge from Democrats pursuing impeachment: that Trump held up U.S. military aid to Ukraine in exchange for investigations into Democrats and Biden’s family, according to The Associated Press.

The hearing begins at 2:30 p.m.

— You can read the transcript of Morrison’s closed-door testimony here.

— You can read the newly-released transcripts of testimony from David Holmes and David Hale here.

— You can read about last week’s public hearings here and here.

— You can read about the rough transcript of Trump’s April phone call here.

— You can read a rough transcript of Trump’s July phone call here.

— You can read the whistleblower complaint that prompted the inquiry here.