FBI investigators have announced they found no evidence of criminality in the new batch of Hillary Clinton emails.
In a letter to members of Congress, FBI director James Comey confirmed the agency had finished its review and said nothing had been uncovered to change its previous position.
In July, Mr Comey said Mrs Clinton had been careless but not criminal in handling sensitive material on her private email server while she was secretary of state.
The issue emerged again when the FBI said it was looking into new “pertinent” emails.
They were reportedly found on the laptop of Anthony Weiner, the estranged husband of Huma Abedin, who is one of Mrs Clinton’s closest advisers.
The development came as the latest poll shows the Democratic candidate has retained a narrow edge over Republican rival Donald Trump in the countdown to tomorrow’s US election.
Clinton was on 44 per cent with Trump on 40 per cent, according to the last NBC News/Wall Street Journal opinion survey. A CNN poll of polls, taking that into account, put Clinton on 45 per cent and Trump on 42 per cent, as the pair embark on final tours of battleground states.
However, Republican national committee chairman Reince Priebus said voter data told him the two candidates were in “a dead heat”.
Veteran NBC newsman Tom Brokaw said: “I’ve never seen the country so fractured as it is now.”
In many states, people have been able to vote in advance, with around a third of ballots already cast.
Whoever becomes the next US president will make history. Mrs Clinton, 68, would be the first female in the top role while, at 70, Mr Trump would be the oldest person to assume the presidency.
The two candidates have fought one of the most contentious political races of all time. Their campaigns have been dogged by controversies ranging from sexual assault allegations against Mr Trump to FBI investigations into Mrs Clinton’s email use.
Mrs Clinton aimed to hit high notes yesterday, hoping an uplifting message would wash away voters’ disgust with the gruelling contest. Mr Trump vowed he and his supporters would never quit as he charged into unexpected territory.
With the polls showing her still just ahead of Mr Trump, Mrs Clinton enlisted allies and A-listers for help at stops in Pennsylvania, Ohio and New Hampshire.
She planned to campaign with Cavaliers star LeBron James in Cleveland, and rally voters in Manchester with Khizr Khan, the Gold Star father whose indictment of Mr Trump delivered an emotional high point for Democrats. Mr Trump had a marathon itinerary on the campaign trail lined up, with stops in five states, including Minnesota, Michigan and Pennsylvania. These have long proven unfriendly territory for Republican presidential candidates.
But buoyed by a late surge of momentum, Mr Trump declared that his loyal, white working-class voters would deliver an upset.
Campaign manager Kellyanne Conway said he planned to keep up the break-neck campaign pace through to election day.
After voting in New York, Trump was expected to return to Pennsylvania, Michigan, Ohio, North Carolina and New Hampshire.
Vice-presidential candidate Mike Pence said: “Our secret weapon is the American people who are saying ‘Enough is enough’.”
The Clinton campaign said it is focusing on securing its firewall in the West and upper Midwest.
Clinton started her day with the largely African American congregation of Mount Airy Church of God in Christ in Philadelphia.
A weekend highlight had been her appearance with pop singer Katy Perry.
“Tonight, I want to hear you roar,” a smiling Clinton said before introducing her performance in Philadelphia.
Perry, who hugged the Democratic candidate while wearing a purple cape bearing the words, “I’m with Madam President,” shouted, “In three days, let’s make history!”