Public hearing of the U.S. House Select Committee to investigate the January 6 Attack on the U.S. Capitol

Who is Matthew Pottinger and why is he testifying in the Jan. 6 hearings?

Matthew Pottinger, the deputy national security adviser in the Trump White House, testified that the 2021 insurrection at the Capitol was damaging to national security, at the eighth public hearing of the Jan. 6 Committee on July 21.

WATCH: Jan. 6 Committee hearings – Day 8

The hearing focused on the actions of former President Donald Trump during the Jan. 6 attack on the Capitol, especially on the 187 minutes – or nearly three hours – during which the president did not condemn the violence or ask the rioters to stand down.

Pottinger was also in the White House during much of the afternoon of Jan. 6, and, according to his testimony, tried to convince chief of staff Mark Meadows that Trump needed to diffuse the crowd.

In his testimony to the committee, he said that he decided to resign from the administration, where he’d worked since the beginning of Trump’s term, when he saw the president’s 2:24 p.m. tweet deriding Vice President Mike Pence.

An aide handed him a sheet of paper with Trump’s tweet on it, Pottinger testified. It “disturbed” him that Trump was attacking Pence for carrying out his constitutional duty, he said.

“I simply didn’t want to be associated with the events that were unfolding at the Capitol,” he said, adding that the tweet added “fuel to the fire.”

Pottinger testified that his boss, former national security adviser Robert O’Brien, asked him to stay in his role until O’Brien returned from a trip, which Pottinger did. He left the next morning.

When asked how the insurrection impacted national security, Pottinger said that presidential transitions are always times of increased vulnerability.

But he also said it allowed countries like Russia, China and Iran to paint a picture of faltering American democracy. And he said allies could similarly worry about the strength of America’s institutions.

“I think it’s incumbent upon us to put their minds at ease, to put our own hearts at ease, by investigating what happened on the sixth and making sure that it never happens again,” he said.

Pottinger has already voluntarily appeared before the committee for closed-door testimony. He testified alongside Sarah Matthews, former deputy press secretary, who also resigned after the Jan. 6 attack.

For more on the key players in the Jan. 6 committee hearings, click here.