Meanwhile Donald Trump, who hinted at a 2024 White House bid at a rally in Iowa on Saturday night, recorded his highest ever approval rating in the state, with 53 per cent of Iowans saying they had a favourable opinion of him.

In further troubling news for Democrats, Mr Biden’s support appears to have seen the largest slump among the Democrats’ key constituencies – young people, women and ethnic minorities.

A Pew Research Center survey found Mr Biden’s approval rating among African Americans fell from 85 percent in July to 67 percent in September, while also falling 16 points among Hispanics and 14 points among Asian Americans.

It comes as a leading progressive group warned Democrats that they faced a double threat to their support base ahead of next year’s midterm elections, which will decide the balance of power in Congress.

The fundraising group, Ways to Win, warned in a report that Democrats were experiencing an erosion of support among voters of colour in 11 key states, while Republicans were successfully inspiring first-time voters of colour to turn out at the ballot box.

The report was based on an analysis of almost 65 million voters who took part in the 2020 election in key battleground states.