Republican candidate Donald Trump has said he is going to target states seen as Democratic strongholds in the last two days before the US election.
He will visit Pennsylvania, Michigan and also Minnesota, which has not gone Republican since 1972.
On Saturday evening, he was briefly rushed off the stage by secret service agents at a rally in Reno, Nevada.
Mr Trump had stopped speaking after seeing something in the auditorium, but returned to the stage minutes later.
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.”
There were reports that the man had a gun, but the secret service later said 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, was holding a placard saying Republicans Against Trump when he was tackled by security officials.
“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.
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 suggest that Hillary Clinton has the edge. But history is littered with errant polls and, as we saw today in Reno, unpredictable events.
Earlier, Mr Trump had started off a four-state swing in Florida, where rival Hillary Clinton also campaigned.
She unveiled an advert to run in nearly a dozen states, set to the Katy Perry song, Roar.
Mrs Clinton later appeared with 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.”
Opinion polls suggest Mrs Clinton is still ahead in key states.
But she 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.