President-elect Donald J. Trump on Wednesday replaced his choice for White House counsel before he even got a chance to start the job, a sign of the shifting power dynamics in Mr. Trump’s inner circle in the weeks before he takes office.

David Warrington, the Trump campaign’s top lawyer, is the new pick for White House counsel, Mr. Trump said on social media. William McGinley, whom Mr. Trump chose for the job just weeks ago, is going to move to a role related to the Department of Government Efficiency, which the billionaire Elon Musk will lead.

The move reflects how quickly allegiances can change in Mr. Trump’s orbit. It also came soon after a spate of headlines about one of his top aides, who was accused of trying to profit off his proximity to the president-elect by asking for tens of thousands of dollars in “retainer fees” from potential appointees.

That aide, Boris Epshteyn, has denied the allegations and is still close to Mr. Trump. Although Mr. Epshteyn has no formal role in the transition process, he had sought to influence the staffing of a range of positions across the administration, especially with legal roles like White House counsel, and had endorsed Mr. McGinley.

Mr. Epshteyn had also pushed for Mr. Trump’s most controversial personnel move and the one that quickly became a dramatic failure: Matt Gaetz, the former Republican congressman, who survived eight days as the future attorney general before an investigation into accusations of sexual misconduct and illicit drug use torpedoed his bid.

Wednesday’s announcement of Mr. Warrington reflects a choice that Mr. Trump’s new White House chief of staff, Susie Wiles, had initially preferred, according to two people briefed on the matter. White House counsel is one of the most important lawyers in the executive branch, responsible for advising the president on legal matters across his policy and political responsibilities.