US President Donald Trump and his Democratic challenger Joe Biden are criss-crossing Midwestern states that may hold the keys to the White House in a final burst of campaigning.
Mr Biden went on the offensive in Iowa, a state that voted for Mr Trump by 10 points in 2016.
Mr Trump was making a play for Minnesota, a state that voted narrowly for Hillary Clinton four years ago.
Mr Biden holds a solid national lead ahead of Tuesday’s general election.
But his advantage over Mr Trump is narrower in the handful of US states that could vote for either candidate and decide the outcome in four days’ time.
More than 85 million people have voted early, 55 million of them by post, setting the US on course for the biggest voter turnout in over a century.
Biden snaps at ‘ugly folks’
The Democrat has taken a more measured pace to campaigning than his rival, spending much of the election cycle at his home in Wilmington, Delaware, citing coronavirus restrictions.
But on Friday he sprinted through the states of Iowa, Wisconsin and Minnesota on his busiest day yet.
When Mr Biden was last in Iowa, in January, his presidential campaign was in serious jeopardy after he was defeated in a party vote to pick the Democratic challenger to Mr Trump.
Now Mr Biden could be days away from becoming the 46th president of the United States.
He made a 22-minute appearance at a drive-in event on Friday afternoon in a car park outside the Minnesota State Fairgrounds.
But a throng of Trump supporters turned up and tried to drown him out by honking their horns during his speech.
“There’s a reason they don’t want to hear me,” Mr Biden said, “because they know the president doesn’t say anything, so they’re not used to not hearing anything.”
He was interrupted again later in the speech while urging a national mask-wearing mandate to counter coronavirus.
“This isn’t a political statement like those ugly folks over their beeping their horns,” Mr Biden snapped, eliciting a renewed cacophony of vehicular horns.
The Democrat used many well-honed attack lines on his rival, saying: “Donald Trump has waved the white flag and surrendered to this virus but the American people don’t give up, they don’t cower and neither will I.”
He also added a local pitch to the state’s Somali diaspora.
“That’s why he [Mr Trump] shamelessly equates Somali refugees, folks seeking a better life in America, contributing to this state and our country, with terrorists.” He added: We need a president who will bring us together, not pull us apart.”
Mr Biden’s visit to Minnesota, where he holds a steady lead in opinion polls, was interpreted by some election-watchers as a sign that the Democrat’s campaign was anxious about the state.
The candidate told reporters in Delaware as he set out for the Midwest: “I don’t take anything for granted.”
His campaign war chest, double the size of Mr Trump’s, has won him the luxury of making a play for conservative states such as Iowa and Georgia, where a Democrat has not won the presidency since Bill Clinton in 1992.
Democrats even dream of flipping Texas, which has not voted for one of their presidential candidates since Jimmy Carter in 1976. If Republicans lose the Lone Star state, it would be all but impossible for the party to win the White House again without broadening its voter coalition.
Opinion polls show Mr Biden running Mr Trump close in the ruby red state.
More than nine million Texans have already cast ballots, eclipsing 2016’s turnout there.
Trump refers to Minneapolis unrest
The Republican president is focusing over the last few days on historically Democratic industrial states such as Michigan, Wisconsin and Pennsylvania that he picked up four years ago in his against-all-odds victory.
But on Friday he also headed to Minnesota, which has not voted for a Republican presidential candidate since 1972.
Mr Trump lost the state by just 44,000 votes four years ago. It is one of the few that voted for Mrs Clinton and which Mr Trump is trying to turn this year.
The president acknowledged the steep odds, adding: “But we’re very popular [in Minnesota] because I helped with that disaster in Minneapolis.”
The president was claiming credit for the Democratic governor of Minnesota’s decision to send in the National Guard to quell riots in Minneapolis following the police killing of George Floyd.
In his first stop of the day near the car-making hub of Detroit, Michigan, Mr Trump also said: “A vote for me is to keep and create auto jobs and all sorts of jobs in Michigan, where they belong.”
Mr Trump is planning a head-spinning 13 rallies over the next three days.
His campaign has three such events scheduled in Pennsylvania on Saturday, five in Michigan, Iowa, North Carolina, Georgia and Florida on Sunday, five more on election eve in North Carolina, Pennsylvania, Wisconsin and Michigan.