By Mark Hosenball and John Whitesides
WASHINGTON (Reuters)–FBI Director James Comey came under pressure on Sunday to quickly disclose details of the newly discovered emails related to Hillary Clinton's private server, but the bureau must obtain a search warrant before agents can even examine the emails.
Sources familiar with the matter said the FBI had concluded it could not thoroughly explore the material without additional legal authorization in the form of a search warrant, which would normally require approval from a judge or magistrate.
The process could scuttle any hopes of a swift resolution to the probe, raising the possibility of a prolonged controversy that could extend beyond the Nov. 8 election and cast a shadow over a Clinton transition if she wins the White House.
Comey's disclosure of the new emails on Friday plunged the final days of the White House race between Democrat Clinton and Republican Donald Trump into turmoil. Clinton had opened a recent lead over Trump in national polls, but it had been narrowing even before the email controversy resurfaced.
Prominent Democrats and top aides to Clinton lashed out at Comey for revealing the bureau's probe of the newly found emails and renewed their demands that he quickly release details about the discovery.
U.S. Senate Democratic leader Harry Reid sent a letter to Comey on Sunday suggesting he violated the Hatch Act, which bars the use of an executive branch position to influence an election.
"Through your partisan actions, you may have broken the law," Reid, a senator from Nevada, said in the letter to Comey.
Clinton campaign chairman John Podesta and campaign manager Robby Mook questioned Comey's decision to send a letter notifying Congress of the email review before he even knew whether they were significant or relevant.
Comey's letter was "long on innuendo, short on facts," Podesta said on CNN's "State of the Union" program, and accused the Federal Bureau of Investigation chief of breaking precedent by disclosing aspects of an investigation so close to the election.
"We are calling on Mr. Comey to come forward and explain what's at issue here," Podesta said, adding the significance of the emails was unclear.
"He might have taken the first step of actually having looked at them before he did this in the middle of a presidential campaign, so close to the voting." Podesta said.
Comey's letter was sent over the objections of Justice Department officials. Under standard procedures, the FBI would ask a federal prosecutor working for the Justice Department to seek such a warrant.
But that scenario may be complicated because the Justice Department has signaled its dismay with Comey's decision to publicly disclose the bureau's interest in the newly discovered emails.
FBI officials were unavailable for comment on the status of their investigation.
Trump has highlighted the issue as proof for his argument that Clinton is corrupt and untrustworthy.
'THE WAY TO BEAT CORRUPTION'
"We have one ultimate check on Hillary's corruption and that is the power of the vote," Trump told a rally in Las Vegas on Sunday. "The only way to beat the corruption is to show up and vote by the tens of millions."
Comey, who announced in July that the FBI's long investigation of Clinton's emails during her time as secretary of state was ending without any charges, said in his letter the agency would review the newly surfaced emails to determine their relevance to the investigation of her handling of classified information.
"If there is new information, get it out on the table," Mook said on "Fox News Sunday," adding the emails could be duplicates of previously reviewed emails. "Again, it's been reported these emails may not have been sent or received by Secretary Clinton. We don't know anything."
An ABC News/Washington Post poll released on Sunday showed Clinton with a statistically insignificant 1-point national lead on Trump. About a third of likely voters in the poll said they were less likely to back Clinton given Comey's disclosure.
Sources close to the investigation have said the latest emails were discovered as part of a separate probe of former Democratic U.S. Representative Anthony Weiner, the estranged husband of Clinton aide Huma Abedin.
Weiner is the target of an FBI investigation into illicit text messages he is alleged to have sent to a 15-year-old girl in North Carolina.
Sources familiar with the matter said FBI agents working on the Weiner investigation saw material on a laptop belonging to Weiner that led them to believe it might be relevant to the investigation of Clinton's email practices.
"We never thought we were going to say thank you to Anthony Weiner," Trump told the rally in Las Vegas at the Venetian, a hotel and casino on the famous Las Vegas Strip.
Clinton, who told a Florida rally on Saturday that Comey's letter was "deeply troubling," did not address the issue directly on Sunday but referred vaguely to voters overcoming a "distraction."
"There's a lot of noise and distraction but it really comes down to the kind of future we want and who can get us there," she told a packed gay nightclub in Wilton Manors, Florida, where hundreds of supporters who could not get in lined the streets outside.
"We don't want a president who would appoint Supreme Court justices to overturn marriage equality," she said.