Des Moines, Iowa

It’s beginning to feel a lot like Bernie. With Iowans about to gather in living rooms and school halls to start their unique presidential caucus, Joe Biden’s efforts to keep up with the sprightly 78-year-old senator for Vermont are looking more ever more precarious.

With the former vice-president trapped in Washington by his need to attend the impeachment hearings, Sanders’ razzed-up, celebrity-studded ground troops in the midwestern farm state still seem to be making inroads into Biden’s numbers. The challenger’s grassroots fundraising – small donations from ordinary citizens – is going gangbusters (Sanders’ campaign received more than 900,000 donations in December alone and has received five million since he announced his 2020 bid).

As the first round of the battle for the Democrat presidential nomination plays out, there is a lot at stake. Just four candidates stand a chance. On the radical left of the party, Sanders and Massachusetts senator Elizabeth Warren are the full-fat and diet versions of a social and political revolution.

Their programmes have a lot in common: higher taxes on the super-rich; a head-on assault on Wall Street, digital and healthcare oligopolies; higher minimum wages; and stringent climate action. While Sanders calls himself a “democratic socialist”, Warren claims to “love markets”’ but promises Big Government regulation to make them work better. Both, however, look suspiciously “European” to American conservatives.

In what is increasingly seen as the Democrats’ “establishment” corner, the two-way fight is between Obama’s veep and Pete Buttigieg, the youthful upstart mayor of South Bend, Indiana. By contrast to low-energy Biden – “sleepy Joe” in Donald Trump’s caustic slapdown – dynamic mayor Pete is making waves. But both share the same message about their radical rivals: “This is no time to take a risk” or, as the Biden ads put it: “Let’s nominate the candidate Trump fears the most.” Trump can only be beaten from the centre, they say. Look, after all, at the fate of a similar high-spending radical, Jeremy Corbyn.

The final pre-caucus Iowa poll put Sanders on 28 per cent, with Biden trailing on 21 per cent, and Buttigieg and Warren level-pegging at around 16 per cent. But the caucus system is deceptive. After voters in over 1,500 mini-election venues complete a first round, the votes of those scoring under 15 per cent are redistributed in a second round. No-one knows how that will pan out.

For Biden, the essential task is to stay in the race until the South Carolina primary at the end of the month when his huge support among African-Americans should deliver a comfortable win. By contrast, Sanders needs to consolidate his expected win in New Hampshire next week with a good performance in Nevada mid-month – the “Big Mo” that could sink Biden’s campaign for good. “If Bernie wins Iowa and again in New Hampshire, Biden may not survive until South Carolina,” says Kathie Obradovich, the editor-in-chief of the Iowa Capital Dispatch and a renowned connoisseur of contests.

Stuck in the middle of this dogfight, no-nonsense Iowans are enjoying their four-yearly moment in the sun as the “first in the nation.” Few states could be less representative of melting-pot America. Its 3.1m population is 90 per cent white with black and Hispanic citizens accounting for less than nine per cent of the remainder. More than a third claim German heritage. Iowa’s 87,000 farms – corn, soybeans, dairy and hogs – make it the third-largest food producer in the US.

Yet in six out of the last seven presidential elections, Iowans have backed Democratic candidates – until Trump. Last week, it was easy to see why. While the impeachment proceedings continued on the floor of the Senate, the president jetted into a rapturous reception last Thursday from 7,000 whooping and hollering supporters in state capital Des Moines. And he pushed all the right buttons.

In a rambling 90-minute speech he veered like a truck on black ice all over the political horizon. But, above all, time and again he returned to farming. Though his trade war with China has hit local rural incomes, his brilliantly-timed January armistice with Beijing – guaranteeing a doubling of food sales to the Chinese – allowed him to promise “another colossal victory for the American farmer”.

“The Green New Deal,” he warned, with his usual pantomime hyperbole, “will crush our farms, destroy our wonderful cows…They want to kill our cows. That means you are next.” He added for emphasis: “You better back me or your farms will go to hell.” By contrast, Biden’s endlessly repeated mantra that the election is “about character” feels rather limp.

And then there’s Mike. If Biden fails, the billionaire former New York mayor and media entrepreneur Michael Bloomberg is widely seen as the Democrat establishment’s last resort to prevent a Sanders candidacy.

But it is hard to see how Bloomberg will rally the troops – united only by a desire to rein-in America’s super-rich in favour of the beleaguered middle-class. Few expect any enthusiasm for a polarising candidate whose strongest asset is his wallet.

This weekend, “mini-Mike”, as Trump has dubbed the diminutive late entrant, flexed his monetary muscle by buying an £11m one-minute ad for the coveted Super Bowl TV slot on 2 February. Its message? The case for restricting arms sales and controlling gun ownership – a gift to the National Rifle Association enthusiast in the White House. “That’s going to go down really well with the beer and chicken wings brigade,” a despairing Democrat pundit declared with a sigh.

Ivo Dawnay is a former Sunday Telegraph foreign editor and Washington, D.C., correspondent