DES MOINES — Pete Buttigieg continues to surge in Iowa, leapfrogging Senator Elizabeth Warren and former Vice President Joseph R. Biden Jr. to hold a commanding lead among likely Democratic caucusgoers, according to a new poll from The Des Moines Register and CNN.
The poll showed that Mr. Buttigieg, the 37-year-old mayor of South Bend, Ind., was the first choice for 25 percent of would-be Democratic caucusgoers, a significant increase from the 9 percent he held in September, when The Register last polled the state. The support placed him far ahead of the rest of the field — with the other three top candidates in a virtual tie for second: Ms. Warren, at 16 percent and Mr. Biden and Senator Bernie Sanders at 15 percent.
The results are the latest evidence of Mr. Buttigieg’s strength in Iowa, where his moderate political views, plain-spoken style and military history have resonated in the early voting state. Since September, when he placed fourth in the Register poll, he has more than doubled his on-the-ground staff to over 100 and has opened more than 20 field offices. He recently completed another bus tour in the state.
His rise also suggests that voters, in Iowa at least, are increasingly favoring a centrist agenda — a view that has drawn two new entrants, Deval Patrick, the former governor of Massachusetts, and Michael R. Bloomberg, the former mayor of New York City, — into the race this month.
The poll results reflect the deep split within the Democratic Party over whether it is veering too far to the left to defeat President Trump. Speaking on Friday to a room of wealthy liberal donors, former President Barack Obama expressed concern about some of the policy ideas being promoted by some of the candidates, citing health care and immigration as issues where the proposals may not align with public opinion.
Though he did not single out any candidates directly, his remarks were seen as an implicit criticism of Mr. Sanders and Ms. Warren, two of the leading candidates who are pushing policy plans once considered too liberal, like “Medicare for all,” with the broader goal of “political revolution” and “big, structural change.”
“Even as we push the envelope and we are bold in our vision we also have to be rooted in reality,” Mr. Obama said. “The average American doesn’t think we have to completely tear down the system and remake it.”
Ms. Warren, who led the Register’s September poll, with 22 percent, fell 6 percentage points. Her poll numbers are now roughly what they were in June, when she was at 15 percent. Mr. Sanders, who suffered a heart attack shortly after the last poll results were released, climbed 4 percentage points.
Mr. Biden, who has seen his standing in Iowa slowly slip, dropped 5 percentage points.
In addition to identifying a new Iowa front-runner, the poll has once again delineated a clear divide between the top tier of Democratic candidates — Mr. Buttigieg, Ms. Warren, Mr. Biden and Mr. Sanders — and the rest of the field. The next-closest candidate in the poll was Senator Amy Klobuchar, with 6 percent, followed by a cluster of White House hopefuls with 3 percent, including Senator Cory Booker, Senator Kamala Harris and Andrew Yang.
Mr. Bloomberg, who has suggested he would skip the first four early nominating states, including Iowa, was at 2 percent.