A CENTRAL element of President Trump’s reelection campaign has been the use of his presidential powers to smear Joe Biden and other Democrats with false corruption allegations. The effort began 18 months ago, when Mr. Trump and personal attorney Rudolph W. Giuliani set out to pressure Ukraine’s new president to launch an investigation of Mr. Biden. Despite Mr. Trump’s impeachment for that action, his attempt to leverage his office to bolster his mudslinging has relentlessly continued.

Mr. Trump has pushed the Justice Department to investigate his vague and confused claims that the Obama administration spied on his campaign. He has demanded that former president Barack Obama, Mr. Biden and Hillary Clinton be indicted. He has ordered the political operatives he installed as directors of national intelligence to selectively release information that appears to bolster his false charges. He has even insisted that Secretary of State Mike Pompeo release more of Ms. Clinton’s State Department emails, even though the overblown controversy over them ended with her electoral defeat four years ago.

The relative good news about these gross improprieties is that they are failing to accomplish the president’s aims — as he himself has angrily acknowledged. Ukrainian President Volodymyr Zelensky ultimately refused to launch an investigation of Mr. Biden. This week, The Post reported that an investigation by a federal prosecutor into one of the pieces of Mr. Trump’s “Obamagate” conspiracy theory quietly ended with the conclusion that there had been no misconduct by Mr. Obama, Mr. Biden or anyone else in the “unmasking” of individuals named in intelligence reports.

Attorney General William P. Barr, who has bent over backward to accommodate Mr. Trump’s improper demands, nevertheless has told Republican congressmen that another federal prosecutor’s probe of the FBI’s investigation into possible collaboration between the 2016 Trump campaign and Russia will produce no public report, much less indictments, before Election Day. Even Mr. Pompeo, one of the president’s most loyal retainers, has dodged the demand for more of Ms. Clinton’s emails, most of which were long ago made public.

None of this has deterred Mr. Trump from continuing to air false charges. This week, he once again was relying on Mr. Giuliani, despite warnings from U.S. intelligence agencies that his lawyer has become a channel for Russian disinformation. Mr. Giuliani has actively collaborated with a Ukrainian legislator sanctioned by the Treasury Department as a Kremlin agent seeking to conduct an influence campaign against Mr. Biden. Yet Mr. Trump seized on a dubious story Mr. Giuliani peddled to the New York Post purporting to reveal compromising emails involving Hunter Biden and Ukraine.

Again, the welcome news here is that few outside Mr. Trump’s base and the media who cater to it are taking his slanders seriously. Polls show that Mr. Biden’s favorability ratings have grown rather than diminished during the campaign. Mainstream news organizations and social media have planted red flags around the New York Post story. Mr. Trump clearly hopes that concocted scandals about his opponent will propel him to victory, as they did in 2016. But four years later, his own administration is resisting his attempted abuses — and voters know better than to believe him.

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