US election 2016: Trump rushed off stage by security
Republican candidate Donald Trump was briefly rushed off the stage by Secret Service agents at a rally in Reno, Nevada, in a false alarm.
A man holding a sign saying Republicans Against Trump was tackled by security agents, after shouts that he had a gun.
Mr Trump returned to the stage at Saturday's rally minutes later.
The Republican candidate says he is going to target states seen as Democratic strongholds ahead of Tuesday's election.
Both candidates have been making late changes to their travel schedules as falling poll numbers for Mrs Clinton in some key Democratic-leaning states present what the Trump campaign sees as new opportunities.
However, a new NBC/Wall St Journal opinion poll on Sunday suggested a four-point lead for Mrs Clinton.
The latest Washington Post/ABC tracking poll puts her lead at five points.
Sunday's campaign stops take Mrs Clinton to Ohio, Michigan, Pennsylvania and New Hampshire, while Mr Trump travels to Iowa, Minnesota, Michigan, Pennsylvania and Virginia.
'There is no gun'
On Saturday evening, Mr Trump had stopped speaking at the Reno rally after seeing something in the auditorium.
He was grabbed by two agents, who rushed him off stage, while the protester was held down and searched.
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When he resumed his speech, Mr Trump said: "Nobody said it was going to be easy for us... I want to thank the Secret Service."
The Secret Service later confirmed that someone in front of the stage had shouted "gun", but that "upon a thorough search of the subject and the surrounding area, no weapon was found".
Austyn Crites, the man at the centre of the disturbance, said he was attacked when he brought out his sign.
"I keep repeating - I'm down, someone is trying to choke me - and I'm saying to these people; 'There is no gun, I just have a sign'," Mr Crites explained after the incident.
On Sunday, Donald Trump's campaign manager, Kellyanne Conway, told CNN the protester was a "Democratic plant or operative", although she offered no details.
At the scene: BBC's James Cook in Reno, Nevada
For a moment here in Reno, a political campaign simmering with tension and bubbling with resentment boiled over. As shouts of "gun" rang out and Donald Trump was hustled from the stage there was panic at the front of the packed hall. Some people dived to the floor, others ran for the exits.
A few journalists who left the media pen and headed towards the commotion were treated to manhandling and verbal abuse. There was no gun, of course, and the drama quickly subsided.
Drowned out by the commotion was an allegation of ballot-rigging which Mr Trump had made a few minutes earlier. The Republican claimed that some early voting stations in Nevada had been kept open "for hours and hours beyond closing time" to allow Democratic voters to be brought in by bus.
It was a reminder that this election is already well under way. More than 40 million Americans have voted early. In states which can provide a path to the White House, the data suggests that Hillary Clinton has the edge. But history is littered with errant polls and, as we saw today in Reno, unpredictable events.
Hillary Clinton's chief strategist, John Podesta, said on Sunday that she would focus on Nevada and Michigan, adding that if she won those two in particular, "Hillary Clinton is going to be the next president of the United States."
Mr Podesta also accused Mr Trump of being an advocate of Russian foreign policy and rejecting the bipartisan US approach.
Republican vice-presidential candidate Mike Pence told Fox News Sunday that Mr Trump would accept a clear outcome of the election, although he reserved the right to challenge disputed results.
In the final TV debate with Mrs Clinton, Mr Trump had refused to commit to accepting the result if he lost.
'Tuesday will be fun'
On Saturday evening, Mrs Clinton appeared with Katy Perry at a rally in Philadelphia, Pennsylvania, where the Democratic presidential candidate urged the crowd to vote.
"When your kids and grandkids ask you what you did in 2016," Mrs Clinton said, "I want you to be able to say, I voted for a better, stronger, fairer America."
Perry, who took to the stage to sing the song Nasty, said she was looking forward to election day. "Tuesday's going to be fun," she said, "but Wednesday is going to be better".
Mrs Clinton has seen her lead slip following last week's FBI announcement that it was looking into emails that may be connected to her use of a private email server while she was secretary of state.
More than 40 million early voters have already cast their ballots. Reports suggest many more Latino voters are turning out early in battleground states including Florida, Arizona and Nevada compared to past elections.
Donald Trump told a rally in Tampa, Florida, on Saturday he was "going into what they used to call Democrat strongholds, where we're now either tied or leading. We're going to Minnesota, which traditionally has not been Republican at all".
Pennsylvania and Michigan are also both on his agenda and they too have been tough states for Republicans. They have not won them since 1988.
Florida is an important state, particularly for Mr Trump, with many seeing it as a must-win. Candidates need 270 electoral college votes to win the presidency. Florida is worth 29 and polls suggest the contest is tight.
What is the US media saying?
"Florida, here we are again, right back where we started," writes Anthony Man of South Florida's Sun-Sentinel newspaper. Despite daily visits from presidential candidates or their running mates and more than $115m (£92m, €103m) spent on TV ads, the Sunshine State "is essentially tied and remains the biggest swing state prize" on the eve of the election, as predicted months ago.
The New York Times focuses its attention on Latino voters turning out in large numbers to cast their ballots early, which it calls "a demonstration of political power that lifted Hillary Clinton's presidential hopes and threatened to block Donald J Trump's path to the White House".
Nonetheless, in an editorial, the paper looks towards "the catastrophe that looms if we wake up Wednesday morning to President-elect Trump".
Over at Breitbart, the most-read conservative news website in the US, Patrick Howley writes that Donald Trump is "even surprising the press with his high energy in the final hours of his battle to reclaim American sovereignty". In North Carolina, "Trump tore into Clinton with the clear-eyed precision of a master political assailant".
As the campaign enters its final two days, "to win, Mr Trump needs a whole lot to go right. And to lose, Clinton needs a whole lot to go wrong," writes Kyle Cheney at Politico. In many key states Mr Trump is travelling to this weekend, "millions have already voted early and opportunities to change the campaign's fate are dwindling quickly".