DES MOINES — Senator Bernie Sanders has opened up a lead in Iowa just over a week before the Democratic caucuses, consolidating support from liberals and benefiting from divisions among more moderate presidential candidates who are clustered behind him, according to a New York Times/Siena College poll of likely caucusgoers.

Sanders has gained 6 percentage points since the last Times-Siena survey, in late October, and is now capturing 25 percent of the vote in Iowa. Pete Buttigieg, the former mayor of South Bend, Ind., and former vice president Joe Biden have remained stagnant since the fall, with Buttigieg capturing 18 percent and Biden 17 percent.


The rise of Sanders has come at the expense of his fellow progressive, Senator Elizabeth Warren: She dropped from 22 percent in the October poll, enough to lead the field, to 15 percent in this survey. Senator Amy Klobuchar, who is garnering 8 percent, is the only other candidate approaching double digits.

The changing fortunes of the two liberal candidates, and the secondary position of the two leading centrists, underscores the volatile nature of the Democratic primary after more than a year of campaigning, as voters wrestle with which of the contenders could defeat President Trump. At various times during the past six months Warren and Buttigieg had surged in Iowa, only to fall back, while Biden’s strength has ebbed and flowed here even as he remained at the top of the polls nationally.

But Sanders, a self-described democratic socialist from Vermont making his second run for the White House, appears to be peaking at the right time: This month was the first time he has finished atop a poll in Iowa, after also leading a Des Moines Register-CNN survey two weeks ago. The Times-Siena poll’s margin of error was plus or minus 4.8 percentage points.


Despite Sanders’ ascent, the combined strength of the moderate candidates is unmistakable. The poll showed that 55 percent of those surveyed said they preferred a standard-bearer who is “more moderate than most Democrats.” Just 38 percent said they wanted one who is “more liberal than most Democrats.”

A victory by Sanders in Iowa, where he suffered a narrow loss to Hillary Clinton four years ago, would represent a remarkable comeback for a 78-year-old candidate whose heart attack in October threatened to upend his candidacy. It would also create a moment of high anxiety for establishment-aligned Democrats who are deeply alarmed about a potential Sanders nomination.

Should he prevail in Iowa and face a similarly fractured field of mainstream rivals in New Hampshire, where he also currently leads in the polls, Sanders could be difficult to slow.

Several voters who backed Sanders cited the consistency of his positions over the course of his career, and their ideological alignment with his views.

“Bernie’s authentic,” said Austin Sturch, 25, of Evansdale. “Pretty much everything he’s saying — I can’t put it better than he can.”

Still, much here remains uncertain. Iowa voters are famous for settling on a candidate late, and this year is no different; Sanders, along with the other senators in the race, is pinned down in Washington during Trump’s impeachment trial and unable to campaign here on weekdays. And the final results could turn on two factors that will not be known until caucus night: the size and composition of the electorate, and the preferences of voters whose first choices are eliminated because of the arcane caucus rules.


If the other leading candidates finish bunched together on caucus night on Feb. 3, it is unlikely any of them will drop out of the race after Iowa. Each of the three top hopefuls trailing Sanders has the money to compete in New Hampshire, which is just a week later.

And should no clear moderate alternative to Sanders emerge from the early nominating states, the self-financing Michael Bloomberg, who has already spent more than $260 million on advertising and hired more than 1,000 staff members, is awaiting the field on Super Tuesday in early March.

But first is Iowa, where the race remains up for grabs to an unusual degree so late in the race: In the Times poll, nearly 40 percent of voters said they could still be persuaded to caucus for a different candidate.

Among general election voters in Iowa, a state Trump carried by nearly 10 points four years ago, the president defeated all of the top five candidates as well as Bloomberg in head-to-head matchups. He bested Sanders 48 percent to 42 percent.