This article is from the archive of our partner National Journal

Try as they might, liberal activists are unlikely to persuade Elizabeth Warren to run for president against Hilary Clinton. But grassroots Democrats spoiling for a fight with their business-friendly brethren have a backup plan in mind that offers the next-best thing to a national stage: the California Senate race.

The open-seat race to succeed the retiring Sen. Barbara Boxer gives the party's economic populists their best—and most high-profile—opportunity of 2016 to flex muscle in a Democratic primary. It's little surprise, then, that progressive groups from California to Washington are already scrambling to size up the list of potential candidates in hopes of finding one who fits Warren's unapologetic brand of anti-Wall-Street liberalism.

They have good reason to be excited—and nervous. Against the backdrop of the inability to launch a serious challenge to Clinton, and with few other obvious opportunities on the map next year, a loss in the bluest of states could call into question the wisdom of embracing a populist message. But progressives also know that few states besides the famously liberal California give them a better chance of success, a victory that would earn Warren's wing of the party one of Democrats' most illustrious posts, as well as proof their style of politics can work in the real world.

"I think the California Senate race represents tremendous opportunity for progressives to bring a real strong, new ally," said Neil Sroka, spokesman for the liberal Democracy for America. "Progressive allies are hungry to make sure that happens."

Recent elections have been a checklist of missed opportunities for progressives: In Senate races last year, in nearly every open-seat battleground, Democrats quickly coalesced around the hand-picked nominee of the Democratic Senatorial Campaign Committee and failed to materialize a single meaningful challenge to a sitting senator. Some groups, including DFA and MoveOn.org, have kept hope alive that Warren will change her mind and run for president, but she once again reiterated this week she has no plans to do so. And while Sen. Bernie Sanders's agenda appeals to progressives, he stands little chance of seriously contending with Clinton.

In California, however, they could benefit from a heartier menu of choices—and they're already getting support from the party's populist avatar. Attorney General Kamala Harris received a surprise early endorsement from Wednesday from Warren herself, who praised Harris in an email to supporters as a "smart, tough experienced prosecutor who has consistently stood up to Wall Street."

And Sroka said that although DFA has yet to officially solicit opinions from its members, many early indications suggest they are receptive to a Harris candidacy.

In a long, hugely expensive race expected to draw a handful of serious Democratic candidates, it's unclear if Harris will remain the economic populists' favorite candidate by the time primary day rolls around. The attorney general, who starts as the race's early front-runner overall, was popular with activists before the Warren endorsement, but Democratic strategists suggested she was more popular among the party's mainstream factions.

She's also not the only candidate who could appeal to Warren-style populists. Former Los Angeles Mayor Antonio Villaraigosa is popular with some unions—organizations with far more institutional might in California than liberal groups located in Washington—and is considering a campaign. Tom Steyer, a billionaire environmental advocate, is also weighing a campaign, and although his profile hardly fits that of an anti-Wall-Street crusader, he has showed signs: His first public comments on the race were replete with rhetoric about special interests subverting the democratic process.

"People rail that democracy has been subverted to powerful economic interests—that 'We the People' have been overlooked," he wrote in The Huffington Post. "Based on what I have seen over the last several years, I fear there's some truth in that charge, and it scares me—badly."

All of them will struggle to distinguish themselves with a liberal agenda. It's a given that all of the Democratic candidates will back gay marriage, abortion rights, and a robust environmental agenda.

Perhaps that explains, then, why progressive strategists say their preferred candidate will have to embrace both a vigorous liberal agenda and the temperament of a street-brawler willing to fight for the cause. A confrontational tone, they say, is as important as the policies they support.

"We don't need somebody who just supports the issues that we do," said Steve Smith, spokesman for the California Labor Federation. "We need somebody who champions those issues."

This article is from the archive of our partner National Journal.

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