McDonald’s workers striking across the country Thursday have several demands, including raising their minimum wage to $15 minimum. And one of the policy’s biggest proponents, 2020 presidential candidate Bernie Sanders, emailed his supporters to rally people to the picket lines.

It’s not uncommon for members of the 2020 Democratic field to show up to picket lines or tweet out their support to striking workers. But Bernie is taking labor solidarity to a new level by tapping into his campaign’s massive listservs to mobilize support for striking workers. It’s an extraordinary and possibly unprecedented move, according to labor historians and union organizers.

The Vermont senator's presidential campaign sent geo-targeted emails Tuesday to supporters in or around 10 cities throughout the U.S. to support striking McDonald’s workers, according to the campaign. Employees at the fast-food chain are staging one-day walkouts and other work actions to fight for a $15 minimum wage, union rights, and workplaces free of sexual harassment.

“Bernie Sanders is joining in solidarity with McDonald’s workers in Dallas, and you can do the same right here in Iowa,” reads one of the emails. “Showing up at a picket line for striking workers is an incredible act of solidarity to show that you support their fight for a better life.”

The emails then include an address where picketers are gathering as well as an RSVP link.

Bernie is one of at least four 2020 presidential candidates — along with Sen. Cory Booker, former Secretary of Housing and Urban Development Julian Castro, and Washington Gov. Jay Inslee — who plan to show solidarity on McDonald’s picket lines. In April, candidates like Joe Biden, Elizabeth Warren, and Pete Buttigieg also showed up to Stop & Shop picket lines to support striking grocery store workers.

But campaign data is usually used for events and volunteer opportunities specific to the candidate, which makes Bernie’s unusual and more aggressive than other candidates’.

“This definitely sets a new bar for politicians who want to earn labor's support. We've seen Democratic politicians join workers at high-profile protests and on picket lines for years, especially during election seasons, but those appearances have sometimes felt very transactional in nature,” said Ethan Miller, a longtime union organizer and secretary-treasurer of the Nonprofit Professional Employees Union, IFPTE Local 70, which organizes workers at nonprofits in Washington, D.C.

It remains to be seen how many people will show up, and it’s impossible to tally how many supporters show up as a result of Bernie’s email. His campaign said the idea is to not only gather support for Bernie in his quest for the White House but to build a mass network of progressive-minded activists throughout the U.S.

“We're building the largest volunteer army in the nation not just to win the Democratic nomination, but also to mobilize people to show up in key fights where people's lives and livelihoods are on the line," Claire Sandberg, Bernie 2020 National Organizing Director, said in a statement to VICE News. “We are proud to uphold Bernie’s commitment to workers, and we will continue to activate our supporters and urge them to join picket lines across the country to support the fight for a strong labor movement."

McDonald’s workers also have plenty to fight for: On Tuesday, 25 women in 20 cities filed sexual harassment complaints against McDonald’s with the U.S. Equal Employment Opportunity Commission. They alleged that the company is not doing enough to keep women safe in an environment that constantly opens them up to harassment.

The average McDonald’s worker also makes less than $9 an hour. Bernie has been a longtime proponent of a $15 minimum wage and supported the concept in 2016, while Hillary Clinton refused to do so. Bernie also re-introduced Senate legislation for a $15 minimum wage this year.

Not the first time

Bernie's campaign already used its email list to drum up support for a one-day University of California strike, the Huffington Post reported. (About 1,000 people expressed interest in or committed to going for the strike that affected tens of thousands of workers.) But the McDonald’s strikes are far more spread out throughout the country and could draw bigger numbers.

Bernie has also used his campaign data to rally supporters for Delta, Wabtec, Amazon, General Motors, Disney, and Nissan workers, as well as Los Angeles teachers, according to the campaign.

Presidential candidates have historically been concerned with winning the endorsements of labor leadership. But 2020 candidates are practically tripping over themselves to show their support striking workers. That’s at least in part because of a recent surge in labor strikes in the United States, but it also shows that presidential contenders are getting back to their roots of showing on-the-ground solidarity.

“Back in the day, it was pretty standard practice for liberal Democrats,” said Joshua Freeman, a history professor at the City University of New York’s School of Labor and Urban Studies.

While Bernie won some union endorsements in 2016, several major unions endorsed Hillary Clinton early on. In the 2020 primaries, however, Bernie is facing far more opponents, and major establishment names like Joe Biden are prioritizing big union leadership endorsements as part of their victory strategies.

Bernie’s strategy seems to be more of a direct appeal to rank-and-file workers and the people who support them — in other words, the people who go to the polls to vote for president.

“It seems to me supporting a strike will generally win favor among both the rank and file and union leaders,” Freeman said, “but I think his main strategy is to appeal to the grassroots, including in labor.”