HILLARY CLINTON’S lead over Donald Trump had started to look so assured that perhaps only some unforeseen calamity could prevent her becoming president. Then on October 28th, eleven days before the election, the FBI director James Comey announced that he was, in effect, considering reopening an investigation into Mrs Clinton’s use of a private e-mail server as secretary of state. Perhaps no other issue is so obviously loaded with calamitous potential for her candidacy.

The FBI concluded its investigation into Mrs Clinton’s email arrangements in July, having ruled that she and her aides had been “extremely careless” in exposing classified information to her inexpertly-secured server, but that they had done nothing criminal. In a letter to Congress, however, Mr Comey said that “in connection with an unrelated case” new e-mails had emerged which “appear to be pertinent to the investigation”.

To that bombshell he attached what he presumably intended as a caveat. Mr Comey said the FBI was still trying to “determine whether they included classified information” and otherwise “assess their importance to our investigation”. But in the feverish last stage of an epically ill-tempered presidential cycle, that equivocation was for the birds: this is truly terrible news for Mrs Clinton.

Supporters of Donald Trump were already firmly convinced her behaviour was criminal. That is why Mr Trump assured Mrs Clinton during the second television debate this month that, if he won on November 8th, he would reinvestigate and imprison her over her e-mails. Almost nine in 10 Republicans said Mr Comey was wrong not to have pressed charges against her. His letter to Congress will inevitably make them feel even more justified in that view, representing a grand opportunity for Mr Trump.

Beset by poor polling and allegations of misogyny and sexual abuse—including by a dozen women who claim to have been groped or inappropriately kissed by Mr Trump—he now has legitimate grounds to talk up what is arguably his rival’s biggest weakness. Responding to Mr Comey’s letter, Mr Trump duly saluted the FBI and the Department of Justice that controls it for their “courage to right the horrible mistake that they made”. He also said he considered the affair “bigger than Watergate”. Expect much more of this in the campaign’s closing days.

Mr Trump and his supporters will raise the prospect of Mrs Clinton being indicted shortly after the election. They will also use the kerfuffle to suggest Mr Trump’s alleged misdemeanors are trivial by comparison; one of his accusers is a porn star (“Oh, I’m sure she’s never been grabbed before,” Mr Trump said of her); meanwhile, Mrs Clinton is back in the gunsights of the FBI. And the fact that Mr Comey has just guaranteed himself lifelong notoriety by perhaps influencing the course of a general election will also persuade Trumpkins that he must have some seriously incriminating dope on Mrs Clinton. Perhaps he does.

It is reported that the new e-mails under examination were found as part of an unrelated investigation into Anthony Weiner, the estranged husband of one of Mrs Clinton’s closest aides, Huma Abedin. A former Democratic congressman, Mr Weiner is being investigated after he was found to have sent illicit text messages to a 15-year-old girl; the new e-mails were allegedly discovered on an electronic device belonging to him and Ms Abedin.

Mr Weiner's unwitting role in the scandal looks additionally bad for Mrs Clinton—partly because it will make Mr Trump look good. "I only worry for the country in that Hillary Clinton was careless and negligent in allowing Weiner to have such close proximity to highly classified information," he once said.

There is so far no indication of what the e-mails in question might contain, though Mr Comey will now be under huge pressure, from all sides, to give some indication of this. In a statement implying that Mr Comey was recklessly interfering in the election, Mrs Clinton’s campaign chairman, John Podesta, called on the FBI director to release the e-mails under his consideration.

“Upon completing this investigation more than three months ago, FBI director Comey declared no reasonable prosecutor would move forward with a case like this and added that it was not even a close call,” Mr Podesta said. “It is extraordinary that we would see something like this just 11 days out from a presidential election. The director owes it to the American people to immediately provide the full details of what he is now examining.”

Whether he does or not, this should help the Republicans galvanise their vote. More seriously for Mrs Clinton, who is currently leading Mr Trump by around five percentage points, it has the potential to expand Mr Trump’s support. Because, rather astonishingly, almost a third of Democrats also said Mr Comey was wrong not to have indicted her first time around. That signals both the broader doubts many Democrats have about their nominee—and the acutely effective way in which this scandal has exacerbated them.

Case reports released by the FBI into its investigation suggest Mr Podesta is in fact right in his appraisal. They portray Mrs Clinton’s amateurish e-mail arrangements as largely a product of staggering naivety and extreme technophobia; they were designed to address her need to receive official and personal e-mails on a single Blackberry device, mainly because she did not know how to use a desktop computer. Nonetheless, the scandal, which first broke shortly after she launched her presidential campaign, has been deeply damaging to Mrs Clinton because of the way it seemed to chime with her pre-existing reputation for dishonesty.

That reputation appears to be substantially unwarranted—it is a product of decades of highly politicised scandals from which Mrs Clinton has emerged convicted of no crime. In the light of it, however, she needed to be far more candid about the nature of her e-mail errors than she appears to be capable of. For months Mrs Clinton denied having done anything wrong—before having a begrudging acknowledgement of her blunder, and more begrudging apology for it, wrung out of her by unrelenting negative coverage of the affair.

Absent some serious new evidence of wrongdoing from Mr Comey, Mrs Clinton’s e-mail error was in this sense mainly political. But it is nonetheless deadly serious. Her lead, though still hefty, has been slipping in recent days; it had been over seven percentage points. Now, with this shocking announcement, Mr Comey has just rekindled a small, flickering possibility of victory for Mr Trump.