More: The department's failure to build a criminal case against Mr. Biden and his aides is the latest example of its increasing inability to follow through on Mr. Trump's demands and bring indictments against those he wants to be criminally targeted. Some of those cases were rejected by grand juries, some were rejected by judges and some, like the autopen case, were abandoned by prosecutors.

But the fact that prosecutors even pursued the matter to begin with reflects the degree to which Mr. Trump has sought to use the levers of government to undermine Mr. Biden's presidency by seizing on an unsubstantiated theory: that the pardons Mr. Biden issued in his final months in office were invalid because he did not have the mental capacity to consent to them.