McKinley also testified that he resigned in part due to “the failure, in my view, of the State Department to offer support to foreign service employees caught up in the impeachment inquiry on Ukraine.”

The solicitation of foreign assistance to dig up dirt on former Vice President Joe Biden and other Trump antagonists — a campaign spearheaded by the president’s personal attorney Rudy Giuliani — has been at the center of House Democrats’ impeachment inquiry.

McKinley was just the latest witness to detail serious concerns about the decision to recall Marie Yovanovitch, the former U.S. ambassador to Ukraine whom Trump and Giuliani vehemently criticized. Current and former officials told Congress they believe Yovanovitch’s ouster was politically motivated.

McKinley, according to people familiar with his nearly five-hour closed-door testimony, said he resigned in part after learning that Trump blasted Yovanovitch during his July 25 phone call with Ukrainian President Volodymyr Zelensky. McKinley also said the State Department was not doing enough to shield officials like Yovanovitch from partisan-driven criticisms and pressure, which he believed could undermine U.S. foreign policy objectives.

“I was disturbed by the implication that foreign governments were being approached to procure negative information on political opponents,” McKinley told Congress, according to the former colleague familiar with his testimony. “I was convinced that this would also have a serious impact on foreign service morale and the integrity of our work overseas.”

“Since I began my career in 1982, I have served my country and every president loyally,” McKinley added. “Under current circumstances, however, I could no longer look the other way as colleagues are denied the professional support and respect they deserve from us all.”

Yovanovitch, who is still employed by the State Department, told congressional investigators last week that there was a “concerted campaign” to smear her based on “unfounded and false claims by people with clearly questionable motives.” She also said she believed she was forced out at Trump’s direction. The dynamic that led to her ouster, she said, was causing “this nation’s most loyal and talented public servants” to run for the exits.

McKinley served as ambassador to four countries and has had several postings at U.S. embassies all over the world. He first joined the foreign service in 1982 and is highly respected among the diplomatic corps.

Another former colleague told POLITICO that McKinley did not work directly on Ukraine-related issues but was concerned that standard diplomatic protocols were being sidelined in favor of a Giuliani-led campaign to discredit top U.S. officials who were unwilling to pursue politically motivated investigations of the president’s political opponents.