Elizabeth Warren offered another big show of support for teachers unions on Tuesday, appearing with Chicago teachers as their strike extended into a fourth school day.

“The unions are how we have power. The unions are how we make sure that the needs of every one of our children are heard loud and clear,” Warren said. “I’m here because the eyes of this nation are upon you. They have turned to Chicago for you to lead the way — for you to show how the power of standing together is the power of making real change in this country.”

The event followed the Monday release of the Democratic presidential candidate’s K-12 education plan, which calls for a suite of union-friendly policies, including a big increase in federal spending on public schools, an end to federal support for charter school growth, and making it easier for public employees to collectively bargain.

At the Chicago event, Warren stood alongside American Federation of Teachers President Randi Weingarten, who has praised Warren’s plan. Warren also promised that she would be a friend to teachers unions in the White House, implicitly contrasting herself with the Obama administration — which had a complicated relationship with unions in part thanks to its embrace of testing and new teacher evaluation policies — and the Trump administration, which has tried (but largely failed) to cut federal education spending.

“America’s public schools need a partner in Washington,” said Warren. “Not a partner who’s going to tell them what to do, not a partner who’s going to do high-stakes testing. Not a partner who’s going to pinch pennies. But a partner who’s going to be there to back you up in the critically important work you do every day.”

The Massachusetts senator isn’t the only candidate to have voiced support for striking teachers in Chicago. Former Vice President Joe Biden and former Secretary of Housing and Urban Development Julián Castro both tweeted their support, and Vermont Senator Bernie Sanders attended a Chicago union rally last month before the strike began. When Los Angeles teachers went on strike earlier this year, Sen. Kamala Harris of California also tweeted her support for them as well.

That level of enthusiasm for teachers unions, coupled with Warren and Sanders’ criticism of charter schools, underscores how the politics of education have changed for Democrats over the last few years. Warren’s plan has earned sharp criticism from leaders of charter schools that have won praise — and millions of federal dollars to expand — from presidential administrations of both parties.

“We are disappointed that her plan paints a picture that all charter schools are part of the problem, when public charter networks, like KIPP, are providing a quality education to so many African American and Latinx students and are trying to address the same issues of inequality in our education system,” Richard Buery, the chief of policy and public affairs for the KIPP Foundation, said in a statement. KIPP is the country’s largest nonprofit charter school network.

Asked about that criticism Tuesday, Warren said only, “I believe that public money should stay in public schools.” (Charter schools are publicly funded but privately run.)

Bargaining between the union and Chicago officials appeared to be at a standstill on Tuesday, and union President Jesse Sharkey warned Monday that a quick settlement was “not likely.” Class sizes, staffing levels for school nurses and social workers, as well as pay for veteran teachers and paraprofessionals, have been the key issues at play. The last time the union went on strike, in 2012, it lasted for seven school days.

Looking for up-to-the-minute coverage of the Chicago strike? We’re tracking it here.