National Security Council aide Lt. Col. Alexander Vindman arrives to testify before the House Intelligence Committee on Capitol Hill in Washington, Tuesday, Nov. 19, 2019, during a public impeachment hearing of President Donald Trump's efforts to tie U.S. aid for Ukraine to investigations of his political opponents. (Shawn Thew/Pool via AP)

WASHINGTON (AP) — “It’s Lt. Col. Vindman.”

With that, the Iraq War veteran, his chest flush with ribbons and commendations, tersely reminded Republican lawmakers questioning his judgment and loyalty just whom they were trying to discredit as the impeachment drive against President Donald Trump veered into the personal.

Alexander Vindman: Purple Heart recipient, career diplomat, Army infantry officer. And this: “I am an American.”

Vindman, a Soviet Jewish immigrant, felt it necessary to state his allegiance as he batted away Republican questions about the offers he got to work for Ukraine’s government. “I immediately dismissed these offers,” he said. Still, the queries carried an implicit suggestion of disloyalty.

When the senior Republican on the House Intelligence Committee, Rep. Devin Nunes, looked down from the dais Tuesday and addressed the witness as “Mr. Vindman,” the pushback was unmistakable.

“Ranking member, it’s Lt. Col. Vindman please,” he said.

The exchange highlighted the extent to which identity politics are playing a role in the impeachment investigation against the 45th president on the cusp of the 2020 election year. Trump has fueled the who-are-you nature of American politics ever since he announced his candidacy in 2015 with a declaration that some Mexicans are criminals and rapists.

Trump and his allies tried to identify Vindman and fellow witness Jennifer William, an adviser to Vice President Mike Pence, as “Never Trumpers.”

“I’m not sure I know an official definition of a ‘Never Trumper,'” Williams said, but she rejected the label.

“I’d call myself never partisan,” Vindman said.

Vindman, with his military bearing and increasingly confident performance, presented a special challenge for Republicans struggling to defend Trump’s pressure campaign to get Ukraine to investigate Hunter Biden, the son of Trump’s Democratic rival Joe Biden. Some GOP lawmakers thanked Vindman for his service even as they questioned his loyalty, to the president and the nation.

Even Trump seemed somewhat restrained Tuesday.

“I don’t know him. I don’t know, as he says, ‘Lieutenant Colonel.’ I understand somebody had the misfortune of calling him ‘Mister’ and he corrected them,” Trump said. “I never saw the man.”

Vindman was 3 years old in 1979 when his family fled Ukraine for the U.S. Earlier in his Army career, Vindman served as an infantry officer and did tours in South Korea, Germany and Iraq. In October 2004, he was wounded by a roadside bomb and awarded the Purple Heart.