Donald Trump is not happy. In an eleventh-hour twist that is either anti-climatic or deeply frustrating, depending on your point of view, F.B.I. director James Comey informed Congress on Sunday that after reviewing thousands of new e-mails—“the biggest story since Watergate,” Trump said—he had once again come to the conclusion as he had last summer: Hillary Clinton should not face any criminal charges for her use of a private e-mail server while serving as secretary of state.

Trump—who hailed Comey as a hero when he unexpectedly announced last month that the bureau had discovered a fresh batch of e-mails, shaking up the race—did not take the news well, turning on the F.B.I. director and accusing him of protecting Clinton. “She is being protected by a rigged system. It’s a totally rigged system, I have been saying it for a long time,” Trump said at a campaign rally in Michigan on Sunday evening. “You can't review 650,000 new e-mails in eight days. You can't do it, folks. Hillary Clinton is guilty. She knows it, the F.B.I. knows it, the people know it, and now it’s up to the American people to deliver justice at the ballot box on November 8.”

The thousands of e-mails Trump referred to were found in connection with a separate federal investigation into former congressman Anthony Weiner, who is recently separated from his wife, top Clinton aide Huma Abedin. But nearly all of the pertinent e-mails were quickly found to be duplicates of e-mails already reviewed by the F.B.I., a senior law-enforcement official told NBC News. While some e-mails contained forwarded information marked as classified, none of the e-mails were new, and no additional review or further statements are expected from the bureau.

The conclusion of the renewed F.B.I. inquiry is a major blow to the Trump campaign, which was briefly resuscitated by the weeks of bad headlines for Clinton. Ten days ago, the G.O.P. nominee faced an almost non-existent path to victory and was watching his White House dreams go up in smoke. All that changed, however, after Comey penned his inflammatory letter to the Senate Judiciary Committee announcing the discovery of thousands of e-mails on a computer belonging to Weiner, who is being investigated for allegedly sexting with a 15-year-old girl. The revelation incited a political firestorm and vaulted Trump in the polls. But by reaching the same conclusion it did earlier this summer, the F.B.I. may have clinched a Trump loss by denying the billionaire the one thing that might have guaranteed his victory: the possibility of criminal charges for Clinton.

Still, Trump isn’t giving up the “Crooked Hillary Clinton” narrative. “Hillary Clinton is the most corrupt person ever to seek the office of the presidency of the United States,” he told the crowd in Michigan. “The investigations into her crimes will go on for a long, long time. The rank-and-file special agents at the F.B.I. won’t let her get away with her terrible crimes,” he added, alluding to the revelation last week of a fervent anti-Clinton faction within the bureau. According to one agent, many people at the F.B.I. view Clinton as “the antichrist personified.”