Congressional Republicans who questioned Army Lt. Col. Alexander Vindman during private testimony in the House Intelligence Committee repeatedly tried to push the White House official to reveal the name of the whistleblower whose complaint sparked impeachment proceedings into President Trump, but Vindman insisted he did not know.

“What the Republicans are trying to do, very clearly in their questioning, is try to front-door or backdoor … Colonel Vindman into revealing who the whistleblower is, even though in his testimony he says he doesn’t know,” said Democratic Rep. Debbie Wasserman Schultz of Florida, who was in the room for at least a few portions of the session Tuesday.