Hours before Biden’s speech, the former US president appeared on a radio show where he declared that if elected he would issue full pardons and a government apology to rioters who stormed the Capitol last year.

He also noted he met with some defendants in his office this week and was helping some financially.

“It’s a disgrace what they’ve done to them,” Trump told conservative radio host Wendy Bell. “What they’ve done to these people is disgraceful.”

Against that backdrop, Biden urged voters to use the November 8 midterms as a chance to push back against extremism and violent rhetoric, noting that America was also in danger of losing its standing on the global stage.

“For more than two centuries, America has been a beacon to the world. But as I stand here tonight, equality and democracy are under assault,” he said. “We need everyone to do their part – to speak up, speak out, get engaged and vote.”

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While Biden has adopted a largely conciliatory tone for most of his term, his latest speeches have had a more aggressive edge, calling out sections of the Republicans for “MAGA extremism” and “semi-fascism”.

“Calling out Donald Trump by name is a big deal for Biden,” tweeted Georgetown University professor EJ Dionne, co-author of the book 100% Democracy.

In another speech in Pennsylvania this week, for instance, he cast Republicans as a threat to law and order after sections of the party called for the FBI to be defunded following the search of Trump’s Mar-a-Lago estate.

“You can’t be pro-law enforcement and pro-insurrection. You can’t be a party of law and order and call the people who attacked the police on January 6 ‘patriots’,” he declared.

But the shift in rhetoric has placed the president under attack from critics who now accuse him of trying to further fracture the country. More broadly, Republicans are also keen to highlight issues they see as weaknesses for the Democrats, such as record high inflation rates, the soaring cost of food and fuel, and Biden’s overall age and performance.

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“Joe Biden is the divider-in-chief and epitomises the current state of the Democratic Party: one of divisiveness, disgust and hostility towards half the country,” Republican National Committee chairwoman Ronna McDaniel said in a statement.

Republican minority house leader Kevin McCarthy said Biden owed “millions of Americans an apology”.

“Instead of trying to bring our country together to solve the MANY problems he has created, President Biden has chosen to divide, demean, and disparage his fellow Americans—simply because they disagree with his policies,” he tweeted.

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Biden’s shift in rhetoric coincides with new polling that suggests his party’s fortunes have improved after several legislative accomplishments, such as bipartisan gun reform, record climate change investment, and the lowering of prescription drug prices.

While Biden is not on the ballot, the midterm elections generally represent the first electoral chance Americans have to express their approval or displeasure with the president of the day.

All 435 seats in the House of Representatives will be up for grabs, along with 34 out of the 100 seats in the Senate.

And Pennsylvania is shaping up to be the ultimate battleground state because it is viewed as the Democrats’ best chance of flipping a seat in the Senate, which could help them retain their wafer thin majority in the all-important chamber.

In a sign of the state’s importance, Biden will return to Pennsylvania on Monday for a Labour Day speech in Pittsburgh.

Trump, meanwhile, will hold a rally there on Saturday - his first since the Mar-a-Lago raid - to beef up the prospects of the two candidates he endorsed: celebrity doctor Mehmet Oz, who is running for the Senate, and far-right politician and election denier Doug Mastriano, who is vying to be governor.

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