Mr. Volker, for his part, views himself as blameless, according to people who have spoken with him. He has told associates that the text messages do not capture the whole story.
“Heard from White House — assuming President Z convinces trump he will investigate / ‘get to the bottom of what happened’ in 2016, we will nail down date for a visit to Washington,” Mr. Volker wrote to a top aide to President Volodymyr Zelensky of Ukraine on July 25.
The text seems to show that Mr. Volker understood that pursuing a policy outcome he wanted — setting up a face-to-face meeting between Mr. Trump and Mr. Zelensky in order to reset the relationship — meant using highly questionable means and what critics call an extraordinary abuse of presidential power — to get there.
But Mr. Volker testified to congressional investigators on Thursday that ultimately he advised the Ukrainians to drop the arrangement and that he was, as he has told associates, simply trying to “stop something bad from happening.”
Mr. Volker, friends said, has remained upbeat, committed to the idea that he helped steer Ukraine policy in a successful direction, and that his decision not to sign the “Never Trump” letters and to serve in the Trump administration was, even in retrospect, the right thing to do.
When Mr. Volker joined the administration in July 2017, he was taking on a difficult task under normal circumstances — supporting democracy and reform in Ukraine while deterring Russian aggression. The added burden, friends said, was doing it all under Mr. Trump, a leader who ran a separate off-the-books foreign policy through Mr. Giuliani, and who wanted to maintain a close relationship with Mr. Putin.
In his testimony to Congress, Mr. Volker said he was aware that Mr. Trump viewed Ukraine as a corrupt country full of “terrible people” who were “trying to take me down.” That view, he said, was fueling a “negative narrative” that stood in the way of building a bilateral relationship with the new Ukraine government.