Kurt Volker, a central figure in the impeachment proceedings, today acknowledged mishandling Rudy Giuliani’s push for Ukrainian officials to open a politically charged investigation, saying he didn’t realize that Joe Biden was the target.

“In hindsight, I now understand that others saw the idea of investigating possible corruption involving the Ukrainian company, Burisma, as equivalent to investigating former Vice President Biden,” Volker, who resigned as the State Department’s lead negotiator for Ukraine in September, told lawmakers Tuesday.