This week, the Democratic road to the governor’s office stretched to the picket lines in Riverside County.

On Wednesday, Sept. 6, Lt. Gov. Gavin Newsom and former Los Angeles mayor Antonio Villaraigosa visited members of Service Employees International Union Local 721 striking against county government.

A third Democratic gubernatorial candidate, state Treasurer John Chiang, rallied strikers Thursday. Several hours earlier, Tom Steyer, a billionaire hedge fund manager and philanthropist rumored to be seeking public office, offered encouragement to union members before they marched to county headquarters in downtown Riverside.

In competitive races with low turnout, union support can make a difference in a primary election, said Jack Pitney, a professor of politics at Claremont McKenna College.

“Organized labor is still an important source of grassroots people power,” he said. “Showing up to a union strike sends an important message of solidarity. As the old saying goes, showing up is 80 percent of life.”

Democratic candidates “need labor unions like they need air and water,” said Renee Van Vechten, a political science professor at the University of Redlands.

Union get-out-the-vote efforts and phone banking to boost turnout can be especially helpful to candidates, said Van Vechten and Marcia Godwin, a professor of public administration at the University of La Verne.

SEIU’s strike, which started and ends this week, is meant to call attention to what the union says are unfair labor practices by the county, which has been in talks with SEIU and two other unions since contracts expired last year.

SEIU, which represents about 7,300 of the county’s 20,000 or so employees, also accuses the county of ignoring dangerous workplace conditions that threaten workers at health care facilities.

Union members, who picketed the county hospital in Moreno Valley on Wednesday, started Thursday at the Riverside Convention Center. In a short speech there, Steyer accused Republicans of waging war on labor.

“We will not back down until working people get not just their money, but the respect and dignity that they’ve earned over hundreds of years,” said Steyer, who has been mentioned as a candidate for governor, U.S. Senate and even the presidency.

While he doesn’t need to fund-raise as much, Steyer, who is known for his work fighting climate change, might be trying to broaden his base of support beyond environmentalists, Godwin said.

In an interview, Steyer said his visit wasn’t about currying favor with SEIU.

“This is exactly in line with what I’ve been doing for years,” he said. “If I were doing this for the first time, maybe that cynicism would be appropriate.”

From the convention center, union members – at least 1,000, organizers said – chanted, held signs and used bells and whistles in a march to the County Administrative Center. Once inside, they cheered and hung banners from balconies.

Before they went in, Chiang, who wore a purple shirt — SEIU’s colors — and hiked Mount Rubidoux with former Riverside Mayor Ron Loveridge beforehand, thanked union members. “Every day you make Riverside County and you make the state of California better,” he said.

Afterward, Chiang said as governor, he would balance the needs of labor and state government. “I’ve been fighting for fairness for workers and businesses throughout,” he said.

While he’s a veteran of public office, Chiang “does not have the visibility of Newsom and Villaraigosa, and he surely does not have the bankroll of Steyer,” Pitney said. “So union support would be especially important to him.”

With the primary more than eight months away, “none of the candidates are awash in union contributions yet,” said Rob Pyers, research director for the nonpartisan California Target Book.

“Money and support are obviously a big part of things,” Pyers said. “SEIU’s main political committee spent $6.5 million in 2012 and $7.8 million in 2014 – to mixed results – and there are some 2.5 million workers in California who belong to unions.”

Villaraigosa, who clashed with labor over his support for charter schools, will “most likely have to contend with attacks from the two major teachers unions, as it stands,” Pyers said.

“While he’s unlikely to be organized labor’s favored candidate next year, (his visit with SEIU) seems like an easy move to try to minimize the amount of labor opposition he’ll have to face.”