WASHINGTON, Nov 21 (Reuters) - Hardline Republican Matt Gaetz withdrew his name from consideration as President-elect Donald Trump's attorney general after the former lawmaker faced opposition from Senate Republicans over his past conduct.

Gaetz, who resigned from the U.S. House of Representatives last week, was the subject of an Ethics Committee probe into allegations of having sex with a 17-year-old girl. He has denied wrongdoing.

The nomination was an early test of Trump's power over Congress, where his Republican Party will hold majorities in both chambers next year. Gaetz was disliked by many fellow Republicans for having orchestrated the ouster last year of former House Speaker Kevin McCarthy, throwing the House into chaos for weeks.

Republicans in the Senate had bristled at the idea of being asked to vote on Gaetz without seeing the findings of the House Ethics Committee's investigation into the allegations of sexual misconduct.

Gaetz, in a post on X, said he wanted to avoid becoming a distraction to the incoming Trump administration.

"There is no time to waste on a needlessly protracted Washington scuffle, thus I'll be withdrawing my name from consideration to serve as Attorney General," Gaetz wrote. "Trump's DOJ must be in place and ready on Day 1."

Gaetz, who was nominated last week, faced questions over his qualifications to serve as the country's top law enforcement official and his past conduct. He was investigated by the Justice Department for nearly three years into potential sex trafficking violations, a probe that ended last year without charges being brought.

Trump was also the subject of multiple Justice Department investigations, and faced two federal indictments related to his conduct during and after his 2017-2021 term in office. He has denied all wrongdoing, described the prosecutions as politically motivated and vowed to use the department to go after political enemies when he returns to power on Jan. 20.

Gaetz earned a reputation as a firebrand and loyal Trump ally during his time in the House and his nomination was viewed as an indication Trump would follow through on his vows to use the Justice Department to exact retribution against his foes.

"He was doing very well but, at the same time, did not want to be a distraction for the Administration, for which he has much respect," Trump wrote on Truth Social.

A spokesperson said Trump would "announce his new decision when it is made."

FIRST TO BOW OUT

Gaetz is the first Cabinet-level nominee tapped to serve in Trump's upcoming administration to withdraw, though several have faced scrutiny over past behavior. His resignation from Congress applied both to his current term, and the new term he was re-elected to that would have begun on Jan. 3.

Another Trump nominee, Fox News personality Pete Hegseth, who was tapped as Defense Secretary, has also been engulfed in controversy for alleged sexual misconduct.

Some Republican senators expressed misgivings about his nomination, though none had said publicly they would outright oppose him.

Republican Senator Cynthia Lummis said Gaetz's decision would give Trump the opportunity to nominate an attorney general “with fewer headwinds in the Senate.”

Vice President-elect JD Vance accompanied Gaetz to meetings with Republican senators on Wednesday and Trump previously said he was standing by his nomination.

Allegations of Gaetz's past behavior, the subject of investigations by the Justice Department and the House, hung over his nomination. A Florida attorney said this week that two women testified to the House panel that they were paid for sex with Gaetz and one witnessed Gaetz having sex with a 17-year-old girl in 2017.

“From everything that built up to this point, it doesn't surprise me," Republican Senator Mike Braun said of Gaetz's decision.

Other Republicans expressed disappointment.

"I had a very important relationship with Matt," said Senator Rick Scott, who like Gaetz is from Florida. Scott said he hopes Trump picks "whoever is going to be a fighter for getting the Department of Justice to stop being a partisan entity."

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Reporting by Bo Erickson in Washington and Andrew Goudsward in New Jersey, additional reporting by David Morgan, Richard Cowan, Moira Warburton, Nathan Layne, Alexandra Ulmer, Doina Chiacu and Ismail Shakil; Editing by Scott Malone and Daniel Wallis