Sen. Bernie Sanders, front-runner for the Democratic presidential nomination, announced Wednesday he will return to California on Sunday for a San Jose rally ahead of the Super Tuesday primary elections as a new poll showed him leading a crowded field of rivals in the state.

His campaign said it will have staff at the rally to collect vote-by-mail ballots and turn them in to county registrars — San Jose is in Santa Clara County, which is switching to mailed ballots this year under the state’s 2016 Voter’s Choice Act. The ballots can be returned by mail, postmarked through Election Day, or dropped off at county election offices.

“Our campaign is doing everything we can to educate voters about the easiest ways to cast their ballots for president,” said Bernie 2020 California State Director Rafael Navar. “No Party Preference and independent voters deserve every opportunity to participate in the democratic process, and that’s why we have been on the ground since day one educating Californians about the ins and outs of voting.”

Sanders was last in the Bay Area on Feb. 17 for a rally in Richmond that drew some 10,000 to a former Ford assembly plant. His March 1 rally will be at 1:30 p.m. at 435 S. Market Street in downtown San Jose.

So far, he is the only candidate who has announced a visit to California before next week’s pivotal primary, although former Vice President Joe Biden’s wife, Jill, is making her way to the Golden State this week, with a stop in San Francisco on Friday.

Multiple polls have shown Sanders leading the crowded Democratic candidate field in California. Two weeks ago, a Public Policy Institute of California poll had found Sanders leading with 32 percent among likely voters in the Democratic primary. That was more than twice his nearest rival, Biden, at 14 percent.

On Wednesday, a Change Research poll commissioned by KQED found Sanders was the top choice of 37 percent of likely Democratic primary voters, followed by Sen. Elizabeth Warren with 20 percent, former Vice President Joe Biden with 12 percent and former South Bend, Indiana Mayor Pete Buttigieg with 11 percent. Former New York Mayor Michael Bloomberg, endorsed by San Jose Mayor Sam Liccardo, had 6 percent.

Both Sanders and Warren showed the biggest gains since the group’s January poll, and are the only two above the 15 percent threshold to qualify for statewide delegates. However, candidates also can receive delegates if they receive more than 15 percent of the vote in any of California’s congressional districts.

The Vermont senator also led his Democratic presidential rivals in donations from Californians last month as he raked in more than $25 million in contributions from around the country, according to campaign finance reports released Feb. 20.

Sanders raised the most money from California donors — $2.8 million in donations of more than $200 from the state, more than any other contender, according to a Bay Area News Group analysis.

By comparison, presidential rival and Warren, got $1.2 million in large-dollar California donations and Biden got $816,000. On the Republican side, President Trump raised $378,000 from large-dollar California donors last month.

Change Research surveyed 1,822 likely general election voters in California, including 1,069 likely Democratic primary voters, and 544 likely Republican primary voters, Feb. 20-23. The margin of error was plus or minus 2.3 percentage points for the full sample, 3.4 points for Democratic primary voters, and 4.1 points for Republican primary voters. Change Research reached voters through targeted online ads that pointed respondents to an online survey instrument.

Staff Writer Casey Tolan contributed to this report.