NEWTON, Iowa — To the crowd of Iowans gathered in a school gym on Saturday night, Senator Elizabeth Warren made a request: They should pose a question to the other presidential candidates who come to Iowa seeking their vote.
“Ask them: Where do you get your money?” she said. “Are you getting it from a bunch of millionaires?”
For Ms. Warren, the question highlighted one of the sharpest contrasts she has drawn with most of her top rivals for the Democratic presidential nomination: She has sworn off holding private fund-raisers with wealthy donors. “The best president money can’t buy,” signs and T-shirts for her campaign say.
“I like that very much,” Cheryl Scherr, 63, said afterward, “because that means that she’s not beholden to anybody.”
After five months as a presidential candidate, Ms. Warren is showing signs of success at distinguishing herself in a packed field. She has inched higher in national polls and, at events within the last month, consistently overshot the campaign’s expected amount of attendees.
She has been propelled in part by a number of disruptive choices, most notably the breakneck pace at which she introduces policy proposals. That has helped keep her in the news, put pressure on rivals and provided more opportunities to shore up her campaign’s once-lackluster fund-raising.
But Ms. Warren’s recent strength also highlights the volatile nature of the campaign’s early stages, and how much any candidate must do to overtake Joseph R. Biden Jr. — whose name recognition and status as a former vice president have placed him comfortably in the role of the front-runner.
Ms. Warren has become a favorite candidate among the activist left and is the subject of a viral tweet or video on a seemingly daily basis, but she still trails Mr. Biden by double digits in polls and does not seem to have broken through in New Hampshire, the critical primary state that neighbors her Massachusetts home.
Her ability to raise money over the long haul also remains a major question mark. In the first quarter of the year, before Mr. Biden entered the race, her fund-raising lagged that of four other candidates: Senator Bernie Sanders of Vermont, Senator Kamala Harris of California, former Representative Beto O’Rourke of Texas and Mayor Pete Buttigieg of South Bend, Ind.
Still, interviews with more than two dozen attendees at Ms. Warren’s campaign events in Iowa over Memorial Day weekend suggested that her steady stream of policy proposals was getting voters’ attention. Her “I have a plan for that” campaign slogan has become a rallying cry for supporters.
“That’s going to be her big selling point,” said Joel Williams, 20, a college student who went to see Ms. Warren in Oskaloosa on Sunday. “The specifics that really go to the heart of people’s frustrations with the system as it is.”
“She’s got it all laid out,” said Susan Conroy, 71, a retired lawyer. “She’s got plans, and people are hungry for knowing, ‘Well, what are you going to do about it?’”
Several recent national polls have placed Ms. Warren at the front of the pack of candidates who are clustered behind Mr. Biden and Mr. Sanders. Ms. Warren has gained ground in polls over the past several weeks, while support for Mr. Sanders dipped after Mr. Biden joined the race.
At her events during a three-day visit to Iowa, Ms. Warren wove together the story of her upbringing in Oklahoma with a walk-through of her plans to achieve what she calls “big, structural change,” before taking a handful of questions.
“She was totally comfortable talking about any topic that anyone brought up, and you can tell she loves it,” said Frank Broz, 37, a small-business owner who went to see Ms. Warren in Fairfield. “I feel like any one of those topics, she could have spent another two hours on. That’s very persuasive to me.”
He added of her White House bid, “She has the energy to say, ‘I’m not just willing to do this; I’m dying to get in there.’”
Ms. Warren’s visit over the weekend was her seventh trip to Iowa this year, and her campaign has established a robust presence in the state, with more than 50 paid staff members. Over the past two months, she has also spent more money on Facebook ads in Iowa, an estimated $34,000, than any other candidate, according to Bully Pulpit Interactive, a Democratic communications firm.
In recent national polling, Ms. Warren has shown particular strength with liberals, college-educated voters and those who are paying close attention to the presidential race. In a survey released last week by Quinnipiac University, she was the most popular candidate among Democrats who are very liberal, with support from 30 percent of those voters, compared with 22 percent for Mr. Sanders.
Sophia Coker-Gunnink, 23, who works for a nonprofit and went to see Ms. Warren in Ottumwa, supported Mr. Sanders in 2016. But this time around, she favors Ms. Warren.
“The main thing for me is the plans that she has that are just more thought out,” she said.
Ms. Warren shows no sign of slowing down on that front. Her campaign is expected to release another major policy proposal within the coming week, timed around a trip to Michigan and Indiana — the 19th and 20th states she will have visited during the campaign’s early stages.
Ms. Warren’s campaign has also caught the attention of several liberal groups and unions. Top leaders at the Service Employees International Union, the influential labor group with almost two million members, have pointed to Ms. Warren’s ascendance as a reason to slow their primary endorsement process, according to people familiar with the deliberations.
Some leaders at S.E.I.U. wanted to back Ms. Harris early in the primary season, these people said, particularly after her campaign’s strong initial rollout, but the fluid nature of the race has the group’s leaders echoing many rank-and-file Democrats, who feel it is too early to choose sides.
Ms. Warren still faces the long-term challenge of growing her support to include a broader population of Democrats, including nonwhite voters as well as moderates. And she faces obstacles in multiple directions: In addition to competing with Mr. Sanders for voters on the party’s left flank, she faces stiff competition from other candidates to emerge as an alternative to Mr. Biden, whose centrist campaign could appeal to a broad swath of Democratic voters.
Like others in the race, she is dealing with the so-called electability test, as voters assess which candidate they believe is best suited to defeat Mr. Trump — a calculation that can include gender bias in a country that has never elected a female president. Some online supporters have even taken to calling her “Likable Liz” in an attempt to rebuff notions she is only a policy wonk.
“I think she is somebody who could be a great candidate,” said Ann Visser, 62, a retired high school teacher who saw Ms. Warren in Oskaloosa. “I think there are some hurdles. I think that we have to get over this idea that a woman cannot be the president of the United States.”
Then there is the looming question of Ms. Warren’s fund-raising. Her decision to swear off high-dollar events distinguishes her in the sprawling field and dovetails well with one of the main planks of her campaign platform, which focuses on fighting corruption.
“Now is the time that Democrats had better be walking the walk, not just talking the talk,” Ms. Warren told the crowd in Newton after urging them to ask other candidates whether they were getting their money from millionaires.
At the same time, the decision carries risks for the financial viability of her bid. Ms. Warren is counting on online donors to sustain her campaign operation for the long haul, even as other candidates like Mr. Biden, Ms. Harris and Mr. Buttigieg pile up campaign cash from big donors in addition to online contributors.
For now, Ms. Warren has financial leeway because she transferred about $10 million to her presidential bid from her Senate account. But she struggled with early fund-raising, and her campaign burned through cash in the first quarter of the year, building a payroll that was far larger than that of any other Democratic candidate.
Mr. Biden, in particular, has relied on traditional high-dollar fund-raisers in the early days of his presidential bid. Ms. Warren declined to name names when asked by a reporter if she believed any specific candidates were not “walking the walk,” as she had put it.
“I know the race that I’m running,” she said, “and I’m proud to be running it.”