There is, in fact, no evidence that President Biden has had any role in the investigation. Mr. Biden has not publicly demanded that the Justice Department lock up Mr. Trump the way Mr. Trump publicly demanded that the Justice Department lock up Mr. Biden and other Democrats. Nor has anyone knowledgeably contradicted the White House statement that it was not even informed about the search at Mar-a-Lago beforehand, much less involved in ordering it. But Mr. Trump has a long history of accusing adversaries of doing what he himself does or would do in the same situation.

His efforts to politicize the law enforcement system have now become his shield to try to deflect accusations of wrongdoing. Just as he asserted on Monday that the F.B.I. search was political persecution, he made the same claim on Wednesday about the New York attorney general’s unrelated investigation of his business practices as he invoked his Fifth Amendment right to avoid testifying because his answers could incriminate him.

“Now to flip the script and falsely claim that he’s the victim of the exact same tactics that he once deployed is just the rankest hypocrisy,” said Norman L. Eisen, who served as special counsel to the House Judiciary Committee during the first Trump impeachment. “But consistency, logic, evidence, truth — those are always the first to go by the board when a democracy comes under assault from within.”