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President Donald Trump’s nominee to lead the Cybersecurity and Infrastructure Security Agency has withdrawn from consideration for the position, the latest blow to the struggling agency and a significant setback for the Trump administration as it tries to establish a bold new cybersecurity agenda.

Sean Plankey informed the Trump administration of his withdrawal on Wednesday, according to four familiar with the matter, who requested anonymity to discuss a personnel issue.

“After thirteen months since my initial nomination, it has become clear the Senate will not confirm me,” Plankey wrote in a letter to the White House and the Department of Homeland Security that was first reported by POLITICO and later published by The New York Times.

Plankey, who until recently served as a senior adviser for Coast Guard affairs at DHS, hinted in the letter that Trump planned to announce a replacement nominee soon.

“While I humbly request the removal of my nomination,” he wrote in the letter, “I wholeheartedly support President Trump’s upcoming nomination for CISA and look forward to the continued success of the United States of America.”

Plankey and the White House did not respond to requests for comment. DHS declined to comment.

Senate stalled Plankey’s nomination

Plankey’s withdrawal caps a tumultuous nomination process.

Cybersecurity experts and industry leaders praised Plankey after Trump picked him in March 2025, but his nomination quickly stalled in the Senate as lawmakers of both parties placed holds on it. The holds had little to do with Plankey himself — Sen. Ron Wyden, D-Ore., objected to CISA’s refusal to release a report on security vulnerabilities in the telecommunications sector, while Sen. Rick Scott, R-Fla., opposed the Coast Guard reducing a contract with a shipbuilder in his state. But the holds nonetheless stymied Plankey’s nomination.

Plankey’s unceremonious exit from his DHS job in March generated negative attention that further diminished his prospects. (He told allies that he voluntarily left his job to resolve Scott’s Coast Guard objection.) Despite Trump renominating Plankey in January after the initial submission expired — a move that CBS News reported was actually an accident — few experts believed that the Senate would confirm him.

In the meantime, CISA was left without a permanent leader as it struggled through personnel cuts and mission downsizing. The agency has seen its reputation among stakeholders crumble as it has shed experts, scaled back services and abandoned once-important functions. Its deputy director, Nick Andersen, is serving as acting director.

Prior to his CISA nomination and DHS job, Plankey held senior technology and cybersecurity roles at several companies. During the first Trump administration, he worked on maritime cybersecurity policy at the National Security Council and served as the No. 2 official in the Department of Energy’s cybersecurity and energy security division.

Editor’s note: This story has been updated with independent confirmation of Plankey’s withdrawal.