Sen. Elizabeth Warren (D-Mass.) waves as she gives the morning keynote speech at the Phoenix Convention Center. (Cheryl Evans/AP)

There were plenty of reminders here Friday of why progressive Democrats have been pining for Elizabeth Warren to run for president.

In a fiery speech at Netroots Nation, the country’s largest gathering of progressive activists, the senator from Massachusetts railed against Wall Street “banksters” who deserve to be in jail. She decried an economic system “rigged for the rich and powerful.” And she vowed to fight an “insider Washington” that doesn’t realize how progressive the country really is.

Tucson software engineer Dirk Arnold responded with a standing ovation, joined by most of the 3,000 others in attendance.

Arnold, who wore a Warren T-shirt, said he was mindful of what could have been if his hero had acquiesced to those trying to draft her to run for president. But, he added, he’s moved on.

“My switch has flipped over to Bernie,” Arnold said, referring to Sen. Bernie Sanders, the self-described democratic socialist from Vermont who has emerged as the leading alternative to Hillary Rodham Clinton for the Democratic presidential nomination.

Democratic presidential candidate Sen. Bernie Sanders (I-Vt.). (Charlie Riedel/AP)

That seemed to be the sentiment of many former Warren boosters here for a four-day gathering that Sanders and fellow Democratic candidate Martin O’Malley, a former Maryland governor, are scheduled to address Saturday. (Clinton is skipping the conference.)

While Warren won’t be on the debate stage, her influence on the race is still being felt, leading progressive activists here argued.

“Progressives are looking for a candidate speaking Elizabeth Warren’s rhetoric and embracing her policies,” said Stephanie Taylor, co-founder of the Progressive Change Campaign Committee, a Washington-based group whose agenda overlaps with Warren’s on issues such as debt-free college, expansion of Social Security benefits and Wall Street reform.

Taylor said that Warren’s “role right now is agenda-setting, policy-setting. When she picks a fight, it’s a signal it will be a major one, not only for her but for the party.”

In recent months, Clinton — the Democratic front-runner — has borrowed some Warren catchphrases, including her declaration that the economic system is “rigged” against working families.

But Adam Green, the other co-founder of the Progressive Change Campaign Committee, said it remains to be seen whether Clinton will move beyond slogans to champion bold policies.

Warren made no mention of specific presidential candidates during her speech Friday. But she issued them all a challenge.

“I think anyone running for that job . . . should say loud and clear that they agree: We don’t run this country for Wall Street and mega-corporations,” she said. “We run it for people.”

More specifically, Warren said, the candidates should be asked whether they support a bill introduced by Sen. Tammy Baldwin (D-Wis.) that would prevent Wall Street banks from giving multimillion-dollar bonuses to executives who are departing for government jobs.

Within the hour, O’Malley’s campaign released a statement pointing out that he had already issued a comprehensive plan to crack down on Wall Street that includes his own ideas on “closing the revolving door.”

A spokesman for Sanders said that he “of course” supports Baldwin’s legislation and added that Sanders is co-sponsoring a Warren bill in the Senate that would reinstate the Glass-Steagall Act. The legislation aims to prevent commercial banks from engaging in risky investment schemes.

While many former Warren boosters at the conference said they had found a suitable alternative in Sanders, others were less certain. Several suggested that they’d prefer a female nominee, and some said Warren’s age — she’s 66 — would be less of an issue than Sanders’s age, 73.

But a noticeable number of people wore Sanders T-shirts, and several groups handed out Sanders stickers.

“I think [Warren] would have been an amazing first woman president instead of Hillary,” said Belen Sisa, a 21-year-old activist from Gilbert, Ariz. But Sisa said that she would be happy with either Warren or Sanders as the nominee — and that pairing them on the same ticket would be ideal. “I guess that would be la-la land,” she added with a sigh.

Austen Levihn-Coon, a Washington-based political consultant, said he feels a kinship with Sanders on most issues. But, he said, it remains to be seen whether Sanders can “pull together the machinery to run on a national stage and present himself as a serious candidate.”

As for Warren: “Maybe we’ll see her next time around,” said Levihn-Coon, 30, whose consulting firm specializes in issue-oriented campaigns.

Even as she has passed on a White House bid, Warren has become increasingly influential in the Senate, said Jim Dean, chairman of Democracy for America, a group that was part of the unsuccessful “Run Warren Run” recruitment effort.

“She was, frankly, the go-to person for raising money in the last cycle,” he said. “She’s built power that way.”

Former congressman Barney Frank (D-Mass.), who did not attend the conference, said Warren would have had little to gain by running for president in a field that includes Clinton.

“If Senator Warren had run for president, she would almost certainly not have got the nomination,” Frank said in a phone interview. “Had she got it, it would not have been worth much after all that bloodshed.”

As things stand, Frank continued, Warren “is now in an extraordinary situation. She’s one of the most influential junior members of Congress, and she can make these critiques that get national attention. . . . People listen to her. She’s an enormously influential person.”

Rep. Keith Ellison (D-Minn.), who attended the conference, said both Sanders and Warren stood to benefit from their respective decisions about entering the race.

“Their role is to articulate the frustrations and the hopes of the vast majority of the American people,” Ellison said in an interview. “Their role is to speak to people’s pain and what they’re hoping for.”

David Weigel contributed to this report.