Any Democratic presidential candidate hoping to win the nation’s most populous state needs the grassroots backing of organized labor.

All seven of the candidates who spoke Saturday to a breakfast gathering of 150 Service Employees International Union employees in San Francisco for the California Democratic Party’s convention could be considered union-friendly. But they offered different appeals to win over the activists, from Sen. Bernie Sanders’ fiery call for a national $15-an-hour minimum wage to Mayor Pete Buttigieg’s appeal to their shared values.

Landing SEIU’s support is key, as the union’s 700,000 California members do the political grunt work — knocking on doors and phone banking — that are the life blood to a campaign, especially for out-of-state candidates who haven’t already built networks in California. SEIU’s support is also an inroad to California’s Latino community, as 40 percent of the union’s members are Latino.

Former Rep. Beto O’Rourke brought the audience to its feet, speaking mostly in Spanish, by promising to end the “bondage” that undocumented immigrants face by giving them a pathway to U.S. citizenship.

“The nearly 11 million undocumented, working some of the toughest jobs in America today ... their immigration status is being used to keep them in a modern-day bondage,” O’Rourke said. “We’re going to free them from any fear from deportation and let them come out into the light.”

Minnesota Sen. Amy Klobuchar played up her background as the granddaughter of a union iron worker and the daughter of two union-member parents. She said she could help Democrats win those “hard places” in the Midwest that they lost in 2016.

“When I am leading this ticket, we’re not going to leave the Midwest behind. We’re not going to leave our workers behind,” Klobuchar said. “If you think we can’t win those hard states and take back the White House in 2020, I’ve got four words for you: Former. Governor. Scott. Walker” of Wisconsin, the Republican who was defeated in a re-election bid last year.

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Washington Gov. Jay Inslee focused on his championing of paid family leave, gender pay equity and a public option for health care. He barely mentioned climate change, the centerpiece of his campaign.

“And because we’ve done these things, we’ve got the best economy in the United States,” Inslee said of his home state. “We have blown up the trickle-down myth of Donald Trump and the Republicans because we’re building a middle class in Washington.”

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Buttigieg said that “even though this president is deservedly unpopular, it is going to be critically important for us to have the right strategy or he could win again. And that is why we’ve got to organize around our values. The values that anchor this campaign are the ones you’ve been fighting for all along, like freedom”— like being able to organize a union.

California Sen. Kamala Harris, who has been endorsed by SEIU in her previous campaigns, reminded the union activists of how they “fought together” during the mortgage meltdown.

When she held out as state attorney general for a bigger settlement with banks than what they had agreed to in a national lawsuit involving several other states, “you stood with me,” Harris told the audience. ”Even when top newspapers were opining against me saying, ‘Kamala Harris needs to take the deal.’ You stood with me and we got back $20 billion” from lenders.

“Yet again, I’m asking you to stand with me in a difficult fight,” Harris said. “It’s not going to be easy.”

Joe Garofoli is The San Francisco Chronicle’s senior political writer. Email: jgarofoli@sfchronicle.com Twitter: @joegarofoli