Ex-GOP Rep. Trey Gowdy of South Carolina has signed on to President Trump’s outside legal team in his fight against impeachment by the House.

Gowdy was the chairman of the House Oversight Committee and led one of the congressional investigations of Hilary Clinton and the 2012 Islamic terrorist attacks in Benghazi, Libya, which left US Ambassador Chris Stevens and three others dead.

Gowdy, 55, also emerged as a fierce defender of the president and critic of special counsel Robert Mueller’s probe into Russian election meddling and the president’s campaign.

Gowdy did not seek reelection last year to the seat he had held for eight years, and has since worked as a lawyer and Fox News contributor until Wednesday, when Fox said in a statement that Gowdy had been “terminated and is no longer a contributor.”

Trump is beefing up his defense team as his administration notified the House Tuesday that they would not participate in what it called Democrats’ “illegitimate” impeachment probe.

White House Counsel Pat Cipollone wrote in a letter to House Democratic leaders Monday that their inquiry has processed in a “manner that violates fundamental fairness and constitutionally mandated due process” and “lacks any legitimate constitutional foundation” or “pretense of fairness.”

The letter came the same day Trump intensified his fight with Congress by blocking Gordon Sondland, the US European Union ambassador, from testifying behind closed doors about the president’s dealings with Ukraine President Volodymyr Zelensky.

During a July phone call, Trump asked Zelensky to launch a corruption probe into a political rival, Joe Biden, and his son Hunter Biden, though there is no known evidence that the pair did anything wrong.

The call, which sparked the impeachment proceedings, came at a time the US was withholding nearly $400 million in security aid to Ukraine, which is locked in a war with Russian-backed separatists in the eastern part of the country.

The cash was subsequently released.