Two months ago, Sen. Elizabeth Warren, D-Mass., was commanding support from about one-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 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 Sen. Bernie Sanders, I-Vt., holding onto steady support from 15% to 20% of Democratic voters, most of them liberals. Meanwhile, former Vice President Joe Biden and Pete Buttigieg, the mayor of South Bend, Indiana, have been snatching supporters from 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 have 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 Warren and 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 Warren and 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% of Sanders’ supporters said Warren would be their second choice in the state’s caucus. Roughly 2 in 5 of Warren’s supporters said the same of Sanders.

Sanders has a seemingly unshakable base of support, with 15% to 20% of Democratic primary voters consistently saying they will vote for him, both nationwide and in the earliest-voting states.

So Warren finds herself needing to pick up some of the more moderate voters, many of whom are also considering Biden and Buttigieg.

With voting in Iowa still more than a month away, much remains to be determined: Roughly 3 in 5 Democratic primary voters who expressed a candidate preference in the most recent Quinnipiac poll said they might still change their minds. 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 Warren has flagged significantly since October among older voters and those with incomes under $100,000. Biden has picked up big gains among both groups.

Biden now commands the support of 22% of liberal Democratic voters, roughly even with both Sanders and Warren, and double his numbers with this group two months ago, according to Quinnipiac’s polling.

And Sanders has clipped much of Warren’s support among younger voters. Among Democratic primary voters under 35, her share dropped by 13 points from October to December, while Sanders’ 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 Donald 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 Biden and Buttigieg.

In Iowa, where Warren seemed to have an edge, 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 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 said they are driven by an almost single-minded desire to unseat 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 Biden who is generally seen as the most capable of doing that, though most of the leading Democratic candidates, including Warren, come out ahead in potential matchups with Trump. A Gallup poll last month found that 51% of Democrats said they viewed Biden as the potential nominee with the greatest chance of beating Trump. Sanders and Warren were locked in a virtual tie for a distant second place, with 16% and 15% each.

“For a big chunk of the Democratic electorate, the goal of this election is to have a Democrat who can beat Trump,” McElwee said, adding that head-to-head polls showing Warren performing slightly worse than Biden and 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.

This article originally appeared in The New York Times .