(BBC) US President Donald Trump and his Democratic challenger Joe Biden are criss-crossing Midwestern states that may hold the keys to the White House.

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.

What is Biden doing?

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 was sprinting through the states of Iowa, Wisconsin and Minnesota on his busiest day of campaigning yet.

He kept hammering away at the Republican president on his handling of the pandemic, which has now killed more than 229,000 people in the US.

“One in six businesses is now out of business because he won’t act,” Mr Biden said at a drive-in rally at the Iowa state fairgrounds in Des Moines.

“We cannot afford four more years of Donald Trump.”

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.

His visit to Minnesota, where he holds a steady lead in opinion polls, was interpreted by some election analysts as a sign that the Democrat’s campaign was anxious about the state.

Mr Biden 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 earned him the leeway to make a play for conservative states such as Iowa.

Democrats even dream of flipping Texas, which has not voted for one of their presidential candidates since Jimmy Carter in 1976. 

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. 

What is Trump doing?

The Republican president is focusing over the next couple of days on the historically Democratic industrial states of Michigan, Wisconsin and Pennsylvania that he picked up four years ago in his against-all-odds victory.

But on Friday he was also heading to Minnesota, which has not voted for a Republican presidential candidate since 1972.

It is one of the few states that voted for Mrs Clinton in 2016 and which Mr Trump is trying to turn this year.

Mr Trump 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.”

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