Senior members of the Democratic Party have said FBI director James Comey might have broken the law after he called for a probe into emails potentially tied to presidential candidate Hillary Clinton just days before the US election.
Comey set off a political firestorm late last week after announcing that the FBI would investigate newly discovered emails related to Clinton.
The emails, belonging to Clinton's closest aide, Huma Abedin, came to light during an investigation of her estranged husband, disgraced former New York congressman Anthony Weiner.
The FBI found the emails on computers it seized during an investigation into lewd messages Weiner is accused of sending to an underaged girl.
Nevada Democrat Harry Reid wrote a stinging letter to Comey on Sunday suggesting he may have broken the Hatch Act by informing Congress of the new emails. The Hatch Act prohibits FBI staff from using their position to influence an election.
"Your actions in recent months have demonstrated a disturbing double standard... with what appears to be a clear intent to aid one political party over another," Reid said, adding that through Comey's "partisan actions, you may have broken the law."
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Clinton's running mate, Tim Kaine, called Comey's actions "extremely puzzling," while John Podesta, Clinton's campaign manager, said the FBI should have investigated the new trove of emails before announcing the review.
"To throw this in the middle of a campaign 11 days out just seems to break with precedent and be inappropriate at this stage," Podesta told CNN's "State of the Union" show.
The FBI had said in July that its investigation into Clinton's email practices had concluded with a recommendation of no criminal charges in the matter.
Meanwhile, President Barack Obama said he did not believe Comey was secretly trying to influence the election outcome, the White House said.
White House spokesman Josh Earnest also said he had no "independent knowledge" of how Comey had arrived at his decision to make public the FBI email investigation or "what factors were considered" in his decision to discuss the issue publicly.
However, Michael Hayden, a former director at the CIA, said Clinton bore responsibility for having used a private email server when serving as US secretary of state.
"The original email set-up was the sin," he told Al Jazeera. "Anyone with government experience views that email arrangement to be frankly inconceivable and all the subsequent explanations of it to be incoherent. Now we're here in this dark place."
Al Jazeera's Rosiland Jordan, reporting from Washington, DC, said Comey's announcement was likely to improve Trump's standing in the election.
"This might encourage Trump supporters who had been thinking about staying home because they thought the race was lost. Following this announcement they might now go out and vote," she said.
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Within minutes of Comey's announcement on Friday, Republican presidential nominee Donald Trump used Comey's letter to attack Clinton on the campaign trail.
He said the political system "might not be as rigged as I thought" now that the FBI has decided to investigate new emails found.
At a rally in Manchester, New Hampshire, Trump praised the FBI, saying: "I think they are going to right the ship, folks."
That is a new tune for Trump, who has repeatedly complained that the Washington establishment has rigged the political system against him.
In an average of national polls, Clinton is leading Trump at 48.0 to 44.9 percent.
Source: Al Jazeera News