Two months ago, Senator Elizabeth Warren of Massachusetts was commanding support from about a quarter of Democratic primary voters nationwide, and seemed to be building a coalition that cut across demographics.
While she remains a leading candidate, after a grueling autumn, polling averages show that her support has dipped back into the teens nationwide — as well as in the early-voting states of Iowa and New Hampshire — and she is working to regain momentum.
For Ms. Warren, this reflects a historical quirk to her candidacy: She has been fighting a two-flank war unlike any seen by a major Democratic candidate in the modern era.
To her left, national and early-state polls show Senator Bernie Sanders of Vermont holding onto steady support from 15 to 20 percent of Democratic voters, most of them liberals. Meanwhile, former Vice President Joseph R. Biden Jr. and Pete Buttigieg, the mayor of South Bend, Ind., have been snatching supporters from Ms. Warren across the ideological spectrum.
This is the first presidential race in the past half-century in which two staunchly left-wing candidates have mounted viable, top-tier candidacies for the Democratic nomination. In many ways, this reflects the state of a party whose rank-and-file members has been moving steadily left since the mid-1990s. Last year, a majority of Democrats identified as liberals for the first time on record, according to Gallup polling.
“The Democratic electorate has a larger liberal bloc than it ever did,” Sean McElwee, a co-founder of Data for Progress, said in an interview. “The rise in college education has created a much higher concentration of ideological liberalism, in a way that hasn’t existed in the past as a coalition in the Democratic Party.”
For now, both Ms. Warren and Mr. Sanders appear to be fighting for support from many of the same voters — while refusing to attack each other on the campaign trail.
Both candidates are seen favorably by more than three-quarters of liberal Democratic primary voters, according to national polls like the one released this week by Quinnipiac University. That survey showed that both Ms. Warren and Mr. Sanders remain the most popular second-choice pick for each other’s supporters.
This is particularly salient in Iowa, where election rules force caucusgoers to support their second choice if their preferred candidate falls short of the minimum threshold at their caucus site. A Des Moines Register/CNN poll last month found that 45 percent of Mr. Sanders’ supporters said Ms. Warren would be their second choice in the state’s caucus. Roughly two in five of Ms. Warren’s supporters said the same of Mr. Sanders.
Mr. Sanders has a seemingly unshakable base of support, with 15 to 20 percent of Democratic primary voters consistently saying they will vote for him, both nationwide and in the earliest-voting states.
So Ms. Warren finds herself needing to pick up some of the more moderate voters, many of whom are also considering Mr. Biden and Mr. Buttigieg.
With voting in Iowa still more than a month away, much remains to be determined: Roughly three in five Democratic primary voters who expressed a candidate preference in the most recent Quinnipiac poll said they might still change their minds. Ms. Warren’s support is particularly fluid, with over two-thirds of her supporters saying they were open to supporting someone else.
Quinnipiac polling shows that Ms. Warren has flagged significantly since October among older voters and those with incomes under $100,000. Mr. Biden has picked up big gains among both groups.
Mr. Biden now commands the support of 22 percent of liberal Democratic voters, roughly even with both Mr. Sanders and Ms. Warren, and double his numbers with this group two months ago, according to Quinnipiac’s polling.
And Mr. Sanders has clipped much of Ms. Warren’s support among younger voters. Among Democratic primary voters under 35, her share dropped by 13 points from October to December, while Mr. Sanders’s rose by 21 points.
To a degree, the drop in support she experienced this fall can be seen as self-perpetuating: Some less-ideological voters got behind her in the late summer and early fall, when she was increasingly being seen as a front-runner. As questions took hold about her viability against President Trump in a general election and how she would fund her proposal for a “Medicare for all”-type health care system, some of those supporters defected to other top candidates, such as Mr. Biden and Mr. Buttigieg.
In Iowa, where Ms. Warren seemed to have an edge, Mr. Buttigieg has pulled ahead in most polls. Both candidates have staked much of their momentum on this first-voting state, and both have opened more than 20 campaign offices there. As Mr. Buttigieg has emerged as the leader of the pack in Iowa, he has argued that he will be able to appeal to potential swing voters in a general election.
Indeed, many Democrats this year say they are driven by an almost single-minded desire to unseat Mr. Trump. In various polls, Democratic voters have indicated that finding a candidate who can defeat the president next November matters to them more than nominating one whose policies gibe with their own views.
Nationwide, it is Mr. Biden who is generally seen as the most capable of doing that, though most of the leading Democratic candidates, including Ms. Warren, come out ahead in potential match-ups with Mr. Trump. A Gallup poll last month found that 51 percent of Democrats said they viewed Mr. Biden as the potential nominee with the greatest chance of beating Mr. Trump. Mr. Sanders and Ms. Warren were locked in a virtual tie for a distant second place, with 16 percent and 15 percent each.
“For a big chunk of the Democratic electorate, the goal of this election is to have a Democrat who can beat Trump,” Mr. McElwee said, adding that head-to-head polls showing Ms. Warren performing slightly worse than Mr. Biden and Mr. Sanders against the president have contributed to her decline. But he cautioned against reading too deeply into the current trends.
“I think Warren actually still has shown that, yes, she has a lot of supporters who are quite fluid, but there’s still a chance in the next two months she can solidify those voters,” he said.