WASHINGTON — The presidential campaign was rocked Friday after federal law enforcement officials said that emails pertinent to the closed investigation into Hillary Clinton's private email server were discovered on a computer belonging to Anthony Weiner, the estranged husband of a top Clinton aide.
In a letter to Congress, FBI director James Comey said the emails had surfaced in an unrelated case, which law enforcement officials said was an FBI investigation into illicit text messages from Weiner to a 15-year-old girl in North Carolina. Weiner, a former Democratic congressman from New York, is married to Huma Abedin, the top aide.
Comey's letter said the FBI would review the emails to determine if they improperly contained classified information, which is tightly controlled by the government. Senior law enforcement officials said it was unclear if any of the emails were from Clinton's private server. And while Comey said in his letter that the emails "appear to be pertinent," the FBI had not yet looked at them.
By the end of a day that brought stinging criticism from both Democrats and Republicans, Comey appeared on the defensive, saying in an internal email to bureau employees that he felt obligated to inform Congress, and "we don't know the significance of this newly discovered collection of emails.''
The new development in the saga over Clinton's handling of classified information came months after the FBI had closed the investigation without charging Clinton. The announcement, less than two weeks before the election, left Clinton's team furious and scrambling for explanations while bolstering the spirits of Donald Trump after a wave of controversies and Republican defections had led many to write him off.
"We are calling the FBI to release all the information that it has," Clinton said adamantly in an evening news conference that took issue with Comey for making the disclosure 11 days before the election. "Let's get it out.''
Trump was ebullient. "Perhaps, finally, justice will be done," he declared at a campaign rally in New Hampshire.
The New York Times, speaking to a senior law enforcement official, reported that tens of thousands of emails belonging to Abedin were on Weiner's laptop, which the FBI had obtained as part of its investigation into Weiner. About a month ago, a person familiar with the investigation told the newspaper, FBI agents seized the laptop as well as Weiner's iPad and cellphone.
Comey said in his letter to Congress that he did not know how long it would take to review the emails. Law enforcement officials said they did not know if and how many were duplicates of emails discovered in the earlier investigation.
Trump has fallen behind Clinton in most national polls and in many key states. Polls have been tightening in recent days, however, as Republicans started returning to their party roots during the final stretch of the race.
An emboldened Trump seized on the FBI action Friday at a rally in New Hampshire. To cheers of "lock her up" from his supporters, Trump said: "Hillary Clinton's corruption is on a scale we have never seen before. We must not let her take her criminal scheme into the Oval Office."
After deriding the FBI for weeks as inept and corrupt, Trump went on to praise the law enforcement agency.
"I have great respect for the fact that the FBI and the DOJ are now willing to have the courage to right the horrible mistake that they made," Trump said, referring also to the Department of Justice. "This was a grave miscarriage of justice that the American people fully understand. It is everybody's hope that it is about to be corrected."
The Clinton campaign called on Comey to provide information beyond what was put forth in the letter.
"Director Comey's letter refers to emails that have come to light in an unrelated case, but we have no idea what those emails are and the director himself notes they may not even be significant," said John Podesta, chairman of Clinton's campaign.
He added: "It is extraordinary that we would see something like this just 11 days out from a presidential election."
Asked in an interview on CNN about Abedin's involvement, Brian Fallon, a spokesman for Clinton, demurred.
"The facts of the matter is stuff that is unknown to us," Fallon said.
As Clinton arrived in Cedar Rapids, Iowa, for an afternoon rally she waved at members of the media gathered on the tarmac but ignored questions shouted in her direction.
The "October surprise" confounded leading Democrats who suddenly found themselves on the defensive.
"This is particularly troubling since so many questions are unanswered," said Sen. Dianne Feinstein of California. "It's unclear whether these emails have already been reviewed or if Secretary Clinton sent or received them. In fact, we don't even know if the FBI has these emails in its possession."
Donna Brazile, the interim chairwoman of the Democratic National Committee, demanded more information from Comey about his next steps and expressed concern about the agency interfering with the election.
"The FBI has a solemn obligation to remain neutral in political matters — even the faintest appearance of using the agency's power to influence our election is deeply troubling," Brazile said.
For Republicans who have struggled to defend Trump amid his sexist comments and conspiracy theories about a rigged election, the opportunity to revisit a controversy that has dogged Clinton was a welcome gift.
The Republican National Committee cheered the new attention on Clinton's emails as a potential turning point in the race.
"The FBI's decision to reopen their criminal investigation into Hillary Clinton's secret email server just 11 days before the election shows how serious this discovery must be," said Reince Priebus, the Republican committee chairman, arguing that the Democratic nominee should be disqualified from seeking the presidency. "This stunning development raises serious questions about what records may not have been turned over and why, and whether they show intent to violate the law."
House Speaker Paul Ryan, who has been critical of Trump, assailed Clinton and said she should no longer be allowed to receive classified briefings.
"Hillary Clinton has nobody but herself to blame," Ryan said. "She was entrusted with some of our nation's most important secrets, and she betrayed that trust by carelessly mishandling highly classified information."
After defending her email practices for months, Clinton sought to put the issue behind her this year, eventually apologizing and acknowledging that using a private server was a mistake.
Clinton and her staff expressed a sense of relief in July when Comey announced that the FBI had closed the investigation after determining that no one should face criminal charges. But he did criticize Clinton and her aides for what he termed the "extremely careless" handling of sensitive information, leaving an opportunity for Republicans to continue hammering her for having bad judgment.
The involvement of Abedin and Weiner in Clinton's case represented an unforeseen twist. Several weeks ago, top Justice Department officials decided that prosecutors in Manhattan would handle Weiner's case. After seizing the devices, investigators have been combing them for information.
It remained unclear whether Comey would reveal more about the contents of the newly discovered emails. In a memo to FBI staff, it was evident that he is keenly aware of the fraught political backdrop that he faces.
"We don't ordinarily tell Congress about ongoing investigations, but here I feel an obligation to do so given that I testified repeatedly in recent months that our investigation was completed," Comey wrote. "I also think it would be misleading to the American people were we not to supplement the record."