Democratic presidential candidate Hillary Clinton, her senior aides and political allies went on the offensive over the weekend against FBI Director James Comey who last week announced a new discovery of emails that he said “appeared to be pertinent” to a previous investigation against her. The FBI had earlier investigated Ms. Clinton’s use of an unauthorised server while she was Secretary of State but did not recommend prosecution.

FBI disclosure in the last fortnight of the presidential campaign – which according to many Republicans amounts to reopening of the investigation – has put a spanner in the works for Ms. Clinton who has appeared increasingly confident to be winning the election. Her Republican opponent Donald Trump seized on the opportunity with glee, hoping to breath fresh air into his campaign that several opinion polls say has been sinking.

“In fact, it’s not just strange; it’s unprecedented and it is deeply troubling,” Ms. Clinton told a rally in Florida, about the FBI action. Using strong words against the FBI chief, her campaign chief John Podesta said his letter to Congressional leaders on the new emails was “long on innuendo and short on facts.” Accusing Mr. Trump of “browbeating the FBI, ” Mr. Podesta said: “indeed, many have speculated that Mr. Comey took this extraordinary action in part to reduce the pressure on him.”

Mr. Trump has been saying the earlier investigation was closed without prosecution because the ‘system’ is rigged in favour of career politicians like Ms. Clinton. He told rallies on Saturday that the FBI has “captured” some of the 33,000 emails that Ms. Clinton had destroyed from her server. “Justice will be delivered, at last,” he said.

According to the FBI, the new emails surfaced when they were investigating former Democratic Congressman Anthony Weiner for exchanging lewd emails with an underage girl. Mr. Weiner, the estranged husband of Ms. Clinton’s most trusted aide Huma Abedin, had on his computer these emails “pertinent” to the Clinton investigation. The FBI has not disclosed how many emails are there or whether they include emails written or received by Ms. Clinton.

In another twist to the story, Mr. Trump said on Saturday that he always believed there was a link between Mr. Weiner and the email investigation. In August 2015 – before Ms. Abedin announced her separation from Mr. Weiner, Mr. Trump had tweeted: “It came out that Huma Abedin knows all about Hillary’s private illegal emails.” “Huma’s PR husband, Anthony Weiner, will tell the world.” On Sunday, several outlets reported that Ms. Abedin has pleaded ignorance of how these emails may have landed on her estranged husband’s computer. Born to Indian father and Pakistani mother, 40-year-old Ms. Abedin is Ms. Clinton’s confidant from the days when she was the first lady.

The Congressional Black Caucus, the group of African American lawmakers that strongly supports Ms. Clinton called Mr. Comey’s action “unusual” and “puzzling.” Congressman Gregory Meeks said: “All it does is gives Republicans a new basis of which to attack Hillary Clinton.” The Democratic National Committee also questioned the timing of the FBI disclosure.

Mr. Comey was formerly a registered Republican – a fact that the Clinton campaign has used in their defence when talking of his decision to not prosecute her earlier. His reputation for being a stickler for rules is formidable, and in one famous instance, he refused to sign off on a surveillance regime as desired by President George W Bush. Mr. Comey, who was then deputy attorney general, wrote his resignation letter instead, forcing Mr. Bush to revise the programme. “Wasn’t it your responsibility to support the president?,” he was asked in an interview in 2014. “No. No, my responsibility, I took an oath to support and defend the Constitution of the United States,” he replied. FBI officials have briefed the media that the director did not want to be holding back the information about the new discovery, and to be accused of a cover up to favour Ms. Clinton.