The strong early showing by Bernie Sanders in back-to-back Democratic contests has raised the prospect of the party nominating its most anti-establishment presidential candidate since George McGovern in 1972, prompting hand-wringing among party leaders increasingly anxious about their chances of defeating Donald Trump in November.
Supporters of the US senator from Vermont have cheered his results in New Hampshire and Iowa — both regarded as swing states in the presidential election — as proof Mr Sanders is winning a new group of voters that may have felt left behind by more traditional Democratic candidates.
“His strength in these primaries and as a candidate comes from a place that Democratic insiders have no view of,” said Neil Sroka of the progressive group Democracy for America.“It’s large swaths of people who are disaffected from the political process.”
Yet several longtime party regulars fret that Mr Sanders has rejected the policies that propelled both Bill Clinton and Barack Obama to the White House, presidencies that help to end almost two decades of Republican dominance of the electoral college.
“I like Bernie. He’s honest, he says what he believes,” said Ed Rendell, the former Democratic governor of Pennsylvania who has supported more centrist candidates such as Joe Biden and Amy Klobuchar. “But he can’t win because America is not going to vote for a socialist.”
His party critics note that Mr Sanders spent most of his congressional career not as a Democrat at all, but as the longest-serving independent in congressional history, and argue he is eschewing a winning formula that helped the party claw back into power in the wake of Mr McGovern’s drubbing at the hands of Richard Nixon.
“[Mr Sanders] is not a Democrat,” said Kenneth Baer, a former Obama administration official and Democratic strategist. “Democrats don’t seem to be taking that seriously. Nobody is actually questioning him. Nobody is actually saying: these are his views on foreign policy, on how we deliver benefits to the least fortunate, and that is not what Democrats believe.”
But Mr Sanders faces an uphill battle if he wants to be the last man standing when the party officially nominates its candidate at July’s Democratic National Convention in Milwaukee, especially if he continues to win over a plurality, rather than a majority, of Democratic voters.
Many Democratic strategists expect moderate voters to gravitate to a single anti-Sanders candidate once others begin to drop out of the race, enabling them to sweep up more delegates as the campaign progresses into the spring.
Zac Petkanas, a Democratic strategist who worked on Hillary Clinton’s 2016 campaign, said Mr Sanders had benefited in Iowa, where he narrowly lost to Pete Buttigieg, and New Hampshire from a crowded field of moderate opponents.
“The reason that people are concerned about him is a lack of consolidation behind an anti-Bernie candidate,” Mr Petkanas said. “Sanders should be very concerned if other candidates are dropping out and start consolidating their support against him. Right now his greatest advantage is he is running against five or six moderates.”
Several of his rivals, including Elizabeth Warren, the US senator from Massachusetts who is regarded as Mr Sanders’ closest rival on the left, have pointed out that both his Iowa and New Hampshire showings fall well short of his vote totals four years ago, where he posted similarly strong results.
Mrs Clinton beat Mr Sanders by the narrowest of margins in Iowa in the 2016 caucuses, and the Vermont senator trounced the former secretary of state in New Hampshire by 22 percentage points.
“In Iowa, Sanders got no more than half the number of people who caucused for him last time, despite spending $11.2m in the state on TV ads — a third more than he spent in 2016,” Roger Lau, Ms Warren’s campaign manager, wrote in a memo released on Tuesday. “In New Hampshire, he is on track to receive around half of his 2016 vote share as well.”
This time around, the 78-year-old was on track to win 26 per cent in New Hampshire, with about 90 per cent of the vote counted.
One Democratic donor, who has given both to Mr Biden, the former US vice-president and Ms Klobuchar, the moderate US senator from Minnesota, warned that a Sanders nomination could doom the party’s chances not just for winning back the White House but also for holding on to the House of Representatives, where many Democrats represent more moderate districts.
“Everybody I know is terrified that Bernie or Elizabeth Warren is going to get traction, and not only would they lose to Trump if you put a socialist label on the Democratic party, we would lose the House,” the donor said. Ms Warren lagged badly with just 9.4 per cent of the vote.
The Sanders campaign is bullish about its upcoming contests, particularly in Nevada, where caucuses will be held on February 22, and where Mr Sanders has gained traction within the state’s Latino community.
He is also showing strength in delegate-heavy California, one of more than a dozen states to vote on “Super Tuesday” on March 3 and where 494 delegates are up for grabs. Mr Sanders is currently polling first in the state with 26 per cent support, according to an average compiled by the website Real Clear Politics.
Still, the possibility of a strong showing from Mike Bloomberg, the former New York City mayor who eschewed the early voting states in favour of spending record sums of his own money on campaigning in Super Tuesday states and beyond, could further muddle the field.
As Mr Biden continues to falter, some centrist Democrats said they were increasingly convinced the nomination would turn into a two-way race between Mr Sanders and Mr Bloomberg, especially if neither Mr Buttigieg nor Ms Klobuchar managed to consolidate the non-Sanders voters.
“[There is a] pretty significant chance that this is going to come down to Sanders and Bloomberg, especially if the non-Bernie lane does not consolidate before Super Tuesday,” said one Democratic strategist, citing Mr Bloomberg’s virtually unlimited funds. (He is worth an estimated $61bn and has already spent more than $300m on his campaign.)
“Bernie will stay in until the bitter end,” the strategist added. “It is the benefit of having a committed, core group of supporters who won’t leave you no matter what.”