His volunteer army is unmatched in the state, and he tallied 46 percent of the vote here in his losing 2016 run. But Sanders' is also facing unpredictable factors, not least of which is who actually votes. Some of Sanders' strongest supporters, including young people and Hispanics, tend to be among the least reliable voters and they are trailing other groups in mail-in ballots returned so far.
At the same time, moderate Democrats are clearing the field for South Carolina primary winner Joe Biden in an urgent attempt to stop the ascent of Sanders, a self-described democratic socialist who centrists fear could doom the party in November.
Amy Klobuchar and Pete Buttigieg are backing Biden after ending their campaigns. California billionaire Tom Steyer exited the race Saturday. State election rules intended to increase participation make it likely that ballot-counting could continue for weeks in close contests. Another unknown: untested former New York City Mayor Mike Bloomberg, who has spent tens of millions of dollars in advertising in the most populous state, is on the ballot for the first time on Super Tuesday, when California is among 14 states with presidential contests.
Four years ago, many Sanders supporters were dejected after his defeat and suspicious of an election process they believe tilted unfairly to Clinton. But his sprawling volunteer corps regrouped, and a candidate once considered on the political fringe has this year accumulated more delegates than any other Democrat so far.
“We were so mistreated at the (2016 Democratic) convention, for him to win California, it would basically thrill us,” said Michael Thaller, a former chair of the California Democratic Party's Progressive Caucus and longtime Sanders supporter.
The swift reordering of the Democratic contest could provide an opening for Biden, who has been lagging in state polls. And he might have another hidden advantage: California prides itself on being the birthplace of the next great thing, but in politics, its voters sometimes look backward and favor the familiar.
For example, in the 2008 Democratic presidential primary, California delivered a comfortable victory for Clinton, who eventually lost the nomination to Barack Obama. Sanders has long considered California among the critical early states, and he capped the California primary campaign with a pair of large rallies Sunday in San Jose and Los Angeles. But his rivals are looking for delegates, too. Massachusetts Sen. Elizabeth Warren is expected to speak Monday in a heavily Hispanic neighborhood near Los Angeles, and Biden planned to be back Tuesday.
President Donald Trump, who lost California by over 4 million votes in 2016, faces only token opposition Tuesday. Meanwhile, congressional and legislative candidates fanned out pursuing votes, including in a series of contested U.S. House districts that could play into control of Congress.
It’s possible the primary could attract about half of the state’s nearly 21 million registered voters. Early voting began in February, and about 22 percent of 16 million mail-in ballots had been returned as of Monday, according to nonpartisan Political Data Inc. Anyone who already voted for Klobuchar, Buttigieg or Steyer can't change their vote.
The long-running tension between the Democratic Party’s progressive wing and its center-left establishment has defined the presidential contest again, as it has for years in many races in California. A Sanders victory would signal a continuing shift to the political left in which voters embrace his “revolution” that includes tuition-free college, breaking up big banks and revamping an economy that has produced a yawning divide between the very wealthy and workaday Americans.
The big change from 2016? Sanders has made inroads with people of color, especially Hispanics, said Sanders pollster Ben Tulchin. In Nevada, support from Latinos, black people and union members, among others, helped him handily win the caucuses.
“We’ve put together a multiracial, diverse coalition that is putting Bernie in a strong position” to win California and a trove of delegates, Tulchin said. California has more than 400 delegates on the line, the most of any state, which are partly divvied up in what amounts to 53 separate elections in congressional districts. A candidate must win 15 percent of the vote in a district to qualify for at least one delegate.
Sanders has pushed back against suggestions that his agenda is pulling the party too far from the center. “I don’t think so, I honestly don’t,” the Vermont senator told California Democrats at a convention last year.
Progressive activist and Sanders supporter Joe Macaluso said the senator’s strong standing in the state was the culmination of years of political organizing. The result: a broad grassroots movement that's battle-tested from the 2016 campaign.
“This is group of experienced activists and organizers in California that ... money can’t buy,” Macaluso said.