Democrats overwhelmingly agree that their top priority in 2020 is to remove Donald Trump from office. But which of the many Democrats running for president is best suited to the task remains a source of deep anxiety and division less than five weeks before the Iowa caucuses.

After more than a year of campaigning, the Democratic presidential primary enters the final sprint before voting begins on 3 February in Iowa in a familiar but fluid state: Joe Biden in the lead, trailed by Bernie Sanders and Elizabeth Warren with Pete Buttigieg also showing signs of strength in the early states.

But, in what has become a quadrennial dilemma for a party prone to fretting over elections, Democrats appear unsatisfied with their choices and worry none of their candidates can beat Trump. A CNN poll from last month found that only 31% of potential Democratic primary voters are very satisfied with the field, the lowest level of its three surveys that asked that question.

Democrats fear Biden is too old, gaffe-prone and does not excite the activist base. They also worry Sanders and Warren are too far left and will alienate moderates. And they worry Buttigieg is too young and inexperienced.

“Suddenly every candidate has clay feet. Voters are worried. There is no perfect candidate but there never is,” said Elaine Karmack, a veteran of Democratic presidential campaigns who studies primaries as a scholar at the Brookings Institution.

Fear of another Trump election has turned Democrats into self-professed pundits, determined to suss out the most “electable” candidate. The perception that Biden is best placed to beat Trump, at least among some voters, has strengthened his resilience despite a series of stumbles and controversies. A central thesis of Biden’s campaign – which he increasingly states in blunt terms on the campaign trail – is that he is the candidate most likely to reassemble a Democratic coalition by appealing to white working class voters who Trump won over in 2016 and to black voters who are critical to the Democratic base.

But rising in second place is Sanders, who rebounded from a heart attack in October and sinking poll numbers earlier this year. His “comeback” has reinforced – and even expanded – his standing among the party’s left wing after months of watching Warren rise to to the front of the pack.

‘The last two candidates standing’

The policy debate and jostling between the party’s many factions has framed much of the contest until this point. Biden and Sanders, the only candidates to have previously run for president, represent the ideological poles of the primary field – and two competing theories of how to beat Trump.

Biden argues Trump is an aberration who can be defeated by the election of a president with the goodwill and experience to unite the country and restore the nation’s standing abroad. Sanders believes Trump is a symptom of an American political system and economy warped by money, greed and inequality. In his view, rooting out Trumpism will require not only a Democratic president but sweeping political and economic reforms.

The divide over which path to take in 2020 has emerged as a central fault line in the Democratic race.

“In this primary we must commit to being aspirational – to really explain what we expect the next president to build not just by refuting what Trump has done but by building a vision for a future that comes after Trump,” said María Urbina, the national political director for progressive group Indivisible. “If you’re not excited to vote for somebody, your neighbors and your friends – everyone who we need to turn out this election to beat Trump’s turnout machine – are probably not going to be very excited to vote for them either.”

In December, Indivisible released a scorecard that ranks the 2020 Democratic field by how closely each candidate aligned with top progressive priorities. The scorecard is a way to signal to its thousands of local organizations which candidates they should back. Warren earned the highest score at 95% while Biden ranked the lowest at 50%.

Warren rose steadily last summer to the top of the field with a registry of plans that would fundamentally remake the US economy but she has receded in recent months amid criticism over her health care proposal. Warren and Sanders, ideological allies whose supporters overlap, are now tangled up for second and third place. Progressive groups are taking sides even as the candidates refuse to go after one another out of fear of antagonizing the other’s supporters, which one of them would need to consolidate to win the nomination.

Moderates, meanwhile, are hopeful that the two will divide the left and keep each other from capturing the nomination. But after years of losing factional feuds, progressives are emboldened by their political prominence in the race.

“The beauty of having more than one progressive candidate in the race is that they have a large, strong base and they have the resources and infrastructure to go all the way into the 2020 calendar year,” said Rebecca Katz, a liberal political consultant. “It’s possible we could be in a situation where they are two of the last candidates standing – and that’s a good thing for the progressive movement.”

Who can beat Trump?

Even as polling paints a steady picture of the primary race, the contest remains far from settled.

Perhaps one of the biggest uncertainties is Michael Bloomberg, the billionaire former New York mayor who entered the race in late November. His strategy for winning the nomination is unorthodox: he won’t contest the early states that every other candidate is scrapping over. Instead, he has poured tens of millions of dollars from his personal fortune into TV and digital advertising into the big, delegate-rich Super Tuesday states going to the polls on 3 March.

But there is plenty of time for other surprises before then.

One of the most significant developments in the race so far came in November, when Kamala Harris, a US senator from California and the only black woman running for president, abruptly ended her campaign.

Her departure sparked a debate among Democrats over how the most diverse primary field in political history has stratified into a top-tier of only white and mostly male candidates.

The discussion briefly boosted fundraising for Cory Booker, the New Jersey senator who is black, and Julián Castro, the former housing secretary who is Latino. But the fleeting attention wasn’t enough to qualify for the December debate, and Castro subsequently dropped out of the race. Tech entrepreneur Andrew Yang, who is polling at 3% nationally and is Asian American, said during the last debate that it was “both an honor and disappointment to be the lone candidate of color” on stage.

No candidate of color has yet qualified for the next debate in January in Iowa, as the first voters prepare to actually cast their ballots.

But the Democrats will now have to compete for media attention with the Senate impeachment trial expected in January. For the senators running for president, this will require time off the campaign trail and in Washington to participate as jurors in the trial.

Several candidates have staked their campaigns on a strong finish in Iowa, including Buttigieg, Sanders and Amy Klobuchar, the US senator from Minnesota. Biden’s team has signaled that it has low expectations for Iowa. Instead, Biden expects to pull ahead in South Carolina, where he maintains a strong base of support among black voters.

On the campaign trail and the debate stage, the candidates will make their closing arguments to voters. After months of debating policy and politics, their final pitches are expected to focus on the issue that matters most to Democrats: why they are the party’s best hope of beating Trump.

“Right now, the biggest priority for Democratic voters is who can beat Donald Trump,” said Michael Starr Hopkins, a Democratic strategist who previously worked on John Delaney’s 2020 presidential campaign.

“It’s not the whole game but it’s the most important part of it because if you thought what Trump did in his first term was bad, imagine what he is capable of in a second term.”