For an eclectic snapshot of the Democratic left, look no further than a squat civic building in downtown Phoenix on Friday night. A loud punk band was packing up, men in uniforms were clearing away vats of orange-and-mint flavored ice water, and stragglers were tucking away thin cucumber slices topped with cheese and bacon bits. The last of the elaborately tattooed young folks were mixed in with the suits, as the party, hosted by a food workers union, wound to a close.

“I’m a long, longtime admirer of Secretary Clinton,” Greg Stanton, the mayor of Phoenix was saying. He wore a jacket, sipped a can of Pabst Blue Ribbon beer and mingled. “I’m probably in the minority here, but mayors across the country are big Hillary fans.”

Surrounded by union organizers and progressive activists, Stanton was definitely the exception. Hillary Clinton may safely be the frontrunner for the Democratic nomination, but at the largest gathering of the liberal grassroots in the country, enthusiasm for her campaign was as mushy as day-old oatmeal. The Netroots Nation conference was much more excited about Vermont Sen. Bernie Sanders, a self-described socialist and populist firebrand.

“It’s a pragmatist versus idealist race,” said Krissi Jimroglou, communications director for Working America, explaining the enthusiasm for Sanders as the union-hosted party cleared out. “This is a very idealist crowd.”

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It didn’t help that Clinton was nowhere to be found. In fact, she was in Iowa and heading to Arkansas, even while her rivals for the Democratic nomination—Sanders and Martin O’Malley—were en route to Phoenix and preparing to court the progressives. The bloggers, unions, teachers, techies, activists, organizers, laborers, musicians and non-profit founders who come to Netroots are the vocal base of the Democratic Party. They’re key for Democrats seeking to winning national elections.

Clinton has sought to attract progressives like these her campaign, many of whom believe that she is too closely connected to Wall Street and corporate interests, and too similar to her centrist husband, President Bill Clinton. The folks at Netroots may well ultimately vote for her in a general election, but for now they’re not enthusiastic about the prospect.

Clinton has talked like a populist and laid out a liberal vision for the country, centering her economic policy around solving income inequality instead of some “arbitrary growth figure” like gross domestic product. She has already called for raising the minimum wage, requiring paid family leave, reducing the cost of college and reining in Wall Street, and she has a host of other progressive policies lined up for the coming months. And she is leading in the polls by large margins, with polls showing her favorability ratings on solid ground.

MORE: Hillary Clinton Will Set Out a Progressive Economic Vision

But the the Netroots attendees are thirsty for specifics. “She’s done a great job explaining the problem: that we have economy that works really well for the top 1% and not everyone else, and we need to fix it,” said Charles Chamberlain, executive director of Democracy for America, the grassroots organization founded by former Vermont Gov. Howard Dean. “Now she needs to detail the policy behind it that puts meat on the bone.”

And even then, they may not be sated. A lot of attendees spoke of a general feeling—a sort of populist touch—which they say they’re not sure Clinton has. Sanders, they say, has it. There was also a widely shared resentment at Netroots that Clinton hadn’t come to kiss the ring. “There’s something people have been looking for that they haven’t been seeing,” said a woman at the Phoenix Convention Center on Friday named Hillary Keyes. She was wearing a button that said “I’m a Hillary for Bernie.” Clinton not coming, Keyes said means for “the people here she loses credibility.”

“We’re disappointed the Democratic frontrunner could miss such a great opportunity,” said Arshad Hasan, chair of the board of directors of Netroots Nation. “The silence from her side makes Bernie shine all the brighter.”

With Clinton gone, the Sanders crowd had full rein. The morning he addressed the crowd, a group dressed as robber barons replete with top hats and bow-ties chanted ironically, “Capitalists for Bernie!” while holding signs saying “Long live the oligarchs!” Others carried huge cutouts of Sanders’ head with a Robin Hood hat.

Clinton’s campaign said their candidate could not attend because of scheduling conflicts—though the organizers set the date for the conference a year in advance. Netroots would have been an unwieldy and raucous stage for Clinton, who tends to favor controlled spaces. And this year was less controlled than usual, as Black Lives Matters protesters derailed the presidential town hall meetings featuring O’Malley and Sanders.

MORE: Sanders and O’Malley Stumble During Black Lives Matter Protest

Despite her absence, Clinton’s ghost defined much of the proceedings here. Sen. Elizabeth Warren, the Massachusetts progressive who is beloved among the Netroots crowd, said in a speech on Friday that all the presidential candidates should move to stop the revolving door between Wall Street and the Cabinet, an applause line that was largely seen as aimed at Clinton. Many of the activists spoke about “moving Hillary to the left,” a common refrain among Democrats.

And activists said at Netroots they could build a huge progressive network to support Clinton in her left-leaning positions. “It is up to everyone in this hall to actually draft a progressive agenda,” said AFL-CIO executive vice president Tefere Gebre in an interview. “And give Hillary Clinton a backbone, or give Bernie Sanders a backbone, or give anyone else a background to govern on that agenda.”

For Clinton, who is establishing her progressive credentials but has not yet managed to capture the imagination of the Netroots demographic, the key will be driving them out in heavy numbers to vote for in a general election. Sanders may know how to rile up the base. But if Netroots is a barometric reading of devotion, then Clinton may have some work to do.

“It’s a degree-of-enthusiasm question,” said Stephanie Taylor, co-founder of the Progressive Change Campaign Committee. “Democratic activists here will probably go out and vote for her. But will they go out to canvass for her, mobilize for her and make calls for her? It really depends on her.”

Meanwhile, on Saturday night, Sanders gave a speech in Phoenix’s convention center, the final big event of the weekend. It was the largest rally of Sanders’ campaign, and 11,300 people streamed through the sand-colored streets of Phoenix and down two long escalators into a cavernous auditorium with the feel of an ocean trench.

Sanders took the stage and delivered his blistering attack on billionaires and the multinational corporations. But first, some context. “When we were coming to Arizona, somebody said Arizona is a conservative state,” thundered Sanders. “What were they talking about?!”

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