WASHINGTON — President Donald Trump on Friday called for the appointment of a special prosecutor to investigate the 2020 election won by Democrat Joe Biden, repeating his baseless claim that the contest was marred by widespread fraud.

“Biden was grossly incompetent, and the 2020 election was a total FRAUD!” Trump said in a social media post in which he also sought to favorably contrast his immigration enforcement approach with that of the former president. “The evidence is MASSIVE and OVERWHELMING. A Special Prosecutor must be appointed. This cannot be allowed to happen again in the United States of America! Let the work begin!”

Trump’s post, made as his Republican White House is consumed by a hugely substantial foreign policy decision on whether to get directly involved in the Israel-Iran war, is part of an amped-up effort by him to undermine the legitimacy of Biden’s presidency. Earlier this month, Trump directed his administration to investigate Biden’s actions as president, alleging aides masked his predecessor’s “cognitive decline.” Biden has dismissed the investigation as “a mere distraction.”

The post also revives a long-running grievance by Trump that the election was stolen even though courts around the country and a Trump attorney general from his first term found no evidence of fraud that could have affected the outcome. The Department of Homeland Security’s cybersecurity arm pronounced the election “the most secure in American history.”

It was unclear what Trump had in mind when he called for a special prosecutor, but in the event Attorney General Pam Bondi heeds his call, she may face pressure to appoint someone who has already been confirmed by the Senate. A Justice Department spokesman declined to comment Friday.

The Justice Department in recent years has appointed a succession of special counsels — sometimes, though not always, plucked from outside the agency — to lead investigations into politically sensitive matters, including into conduct by Biden and by Trump.

Last year, Trump’s personal lawyers launched an aggressive, and successful, challenge to the appointment of Jack Smith, the special counsel assigned to investigate his efforts to undo the 2020 presidential election and his retention of classified documents at his Mar-a-Lago estate in Palm Beach, Florida. A Trump-appointed judge agreed, ruling that then-Attorney General Merrick Garland had exceeded his bounds by appointing a prosecutor without Senate approval and confirmation, and dismissed the case.

That legal team included Todd Blanche, who is now deputy attorney general, as well as Emil Bove, who is Blanche’s top deputy but was recently nominated to serve as a judge on a federal appeals court.