US President Donald Trump and his challenger Joe Biden pushed their final campaign messages in the key swing state of Pennsylvania after a weekend marked by confrontations between their supporters. Biden has held a steady lead in the “keystone state”, according to a Monmouth University poll released on Monday, which found that 51 per cent of likely voters backed Biden while 44 per cent supported Trump. With more than 2.4 million early votes already cast in the state, pollsters say higher than normal turnout is very likely. Trump staged four rallies in Pennsylvania on Saturday, from the Delaware Valley, where the sprawling suburbs outside Philadelphia provide vote-rich territory, to the central part of the state, where fracking for natural gas and oil is a key industry and campaign issue. He made a final appearance in the state on Monday, in Biden’s hometown of Scranton, and then departed for a rally in Michigan, another battleground state. Biden and his running mate, Senator Kamala Harris, were planning to spend the final day of campaigning in “all four corners of the state”. Tensions between the two campaigns flared over the weekend. The FBI said on Sunday that it was investigating an incident on a Texas highway in which a convoy of Trump supporters surrounded a tour bus carrying Biden campaign staff, slowing it down and leading to the cancellation of two planned rallies. Trump tweeted his support for the pro-Trump convoy on Sunday, saying at a campaign rally that “they were protecting” Biden’s bus. At an event in Philadelphia, Biden, who was not on the bus, said: “We’ve never had anything like this. At least we’ve never had a president who thinks it’s a good thing.” Also on Sunday, vehicles flying Trump campaign banners halted traffic on New Jersey’s Garden State Parkway and jammed the Governor Mario M. Cuomo Bridge, which spans the Hudson River north of Manhattan. Armies of lawyers ready if US election outcome heads to court New Jersey Police Superintendent Patrick Callahan said on Monday that he was working with state officials to obtain video footage of the parkway incident, and may press charges against some of those involved, Politico reported. “There’s plenty of ways for people to make their voices heard, but when they endanger the lives of those out there travelling our highways and byways, there’s really no excuse for it,” Callahan said. “And it gave us great cause for concern.” While Biden has a strong polling lead of 8 to 11 percentage points over Trump nationwide, the US’ unique electoral college system means that the election result will boil down to a few important states, including Pennsylvania and Florida, where the Democratic contender’s lead is narrower, at about 3 percentage points, according to the most recent poll of likely voters by The New York Times and Siena College. Overall, the US election appears to be on track to break records, with a surge in early voting bringing the tally to 94 million by Monday morning, equivalent to more than two-thirds of the 137 million votes cast in the 2016 presidential election. Most states adopted expanded early voting channels, through mail-in ballots or stations for in-person voting ahead of election day, as a public health measure amid the continued spread of the coronavirus throughout the country. Trump’s handling of the pandemic emerged as one of the main factors driving voters, with a Reuters/Ipsos poll last month indicating that some 37 per cent of American adults approved of the president’s handling of the pandemic and 59 per cent disapproved. The president fanned the controversy around his administration’s response to Covid-19 by suggesting at a campaign rally on Sunday that he might fire America’s top infectious disease expert, Dr Anthony Fauci. “Don‘t tell anybody, but let me wait until a little bit after the election,” Trump said at a campaign rally in Florida to a crowd chanting “fire Fauci”. Stevie Wonder and Bruce Springsteen show their support for Joe Biden Trump has consistently resisted calls from Fauci and other public health officials for greater social distancing and use of face masks to control the spread of the contagion. The president’s comments about Fauci, who is the director of the National Institute of Allergy and Infectious Diseases, followed Fauci’s remarks to The Washington Post that the US “could not possibly be positioned more poorly” as cases have recently hit daily records. About 230,000 Americans have died from Covid-19, according to figures compiled by Johns Hopkins University.