Lt. Col. Alexander Vindman, the National Security Council official who has testified to Congress about alleged quid pro quo between President Trump and Ukraine, was a registered Democrat for over a decade, according to public records.

Trump has accused Vindman of being a “Never Trumper,” a charge the NSC official denied on Tuesday.

“I would call myself Never Partisan,” Vindman told the House Intelligence Committee.

Vindman, a 44-year-old Army combat veteran who received a Purple Heart for injuries sustained during an IED explosion in Iraq in October 2004, initially registered as a Democrat in New York in 1994. He was listed as a Democrat at least as recently as 2009, according to public records. In 2012, Vindman registered to vote in Washington, D.C., but did not declare a party.

The colonel has been a key witness for congressional Democrats as they move forward on impeachment proceedings against Trump. Trump is accused of improperly threatening to withhold military aid unless the Ukrainian government agreed to investigate corruption allegations involving Joe Biden’s son Hunter’s work for Ukrainian gas company Burisma.

Vindman told lawmakers he believed Trump’s actions were “improper” and would have been viewed as “an order” by Ukrainian President Volodymyr Zelensky.

He received applause when he praised the United States' free speech protections, noting that they did not exist in his birthplace of the Soviet Union.

"Congressman, because this is America. This is the country I have served and defended, that all of my brothers have served. And here, right matters," Vindman said. The Army is reportedly considering relocating Vindman onto a military base after the NSC official asked the military to review his security situation.

"The Army will make sure he's safe, and the Army is actively supporting any safety needs as deemed necessary," an official said.