Teachers are the new heroes of liberal America. Thousands have walked out of classrooms and packed the state capitols of Oklahoma and Kentucky, weeks after West Virginia teachers launched a state-wide walkout over low pay and a broken insurance system and won most of their demands. The liberal media has embraced the protests, which at first seems natural. Public schools are generally underfunded, after all: Every state in the country faced a teacher shortage at the start of the 2017-2018 school year. And with the loathed Betsy DeVos helming the Department of Education, the future of public education seems to tremble on a precipice.

But liberals haven’t always defended teachers with such fervor, as the historian Corey Robin recently noted at his website. In 2012, many greeted striking Chicago teachers with cynicism and even open hostility. So what has changed?

The teachers’ protests are an important lesson in the ways Donald Trump’s presidency has papered over historical divisions on the left. The Trump era began with massive protests, which had the effect of turning public demonstrations—normally a tactic for activists and workers and unions—into a more mainstream form of civic engagement. It has also coincided with a historic weakening of union power, which has pushed teachers and their representatives away from the negotiating table (with its connotations of backroom dealing) and into the clear open air of the streets. And it has turned protests against the arrayed powers of the dark side into a cause to celebrate—even when a Democratic administration largely ignored similar protests.

Robin provides a few representative examples of the way liberals used to respond to teachers’ strikes. Former Time education columnist Andrew Rotherham: “Part of this strike, it’s pretty clear, is that the union needed to have some theater for its members, let them blow off some steam, and that’s increasingly obvious.” Robin added, “I got into a Twitter spat with ABC News’s Terry Moran, who tweeted, ‘I wonder if the Chicago teachers realize how much damage they are doing to their profession—and to so many children and their families.’”

The fear that such strikes would defeat their own purposes and damage teachers’ allies was not limited to the media. It struck the Democratic Party, too. When Chicago teachers went on strike in 2012, demanding fair evaluations, protections for their health benefits, and basic air conditioning in their classrooms, among other things, observers in the press and in the Democratic Party worried about its implications for Barack Obama’s re-election campaign. Days before Chicago teachers even walked out, the Democratic National Committee signed off on a screening of pro-charter school drama Won’t Back Down at the 2012 convention. “Any time we’re fighting among ourselves, it’s never helpful. Any time you waste money and time fighting each other, it’s money we’re not spending fighting our real opponents,” one Democratic strategist told The New York Times.

When teachers did make it out to the picket line, the Obama administration largely stayed mum. Then-Education Secretary Arne Duncan, a tireless supporter of an education reform program that had seen resistance from public school teachers and their unions, eventually released a milquetoast statement that neatly stepped around picking a side.

The faces of the Chicago strike were, as Robin noted, predominately people of color, and as educators they served multiracial student bodies. (The educators in West Virginia, Oklahoma, and Kentucky have been predominantly white.) They also rebelled against a key Obama ally: former White House Chief of State Rahm Emanuel, who had recently been elected the mayor of Chicago and had yet to fall under a cloud for his controversial approach to police violence. Further raising the stakes, Mitt Romney, the Republican nominee for president, wasted no time trying to capitalize on the strike for his own purposes.

But there’s no evidence the strike truly threatened Obama’s prospects. We now know that Obama benefited in 2012 from the perception that Romney, a former private equity titan, was an out-of-touch plutocrat—Romney attacking working teachers would only harden that impression. Furthermore, Americans reliably favor public education over school choice options (though results can differ depending on how pollsters word their questions). Americans also tend to feel more favorably about their local communities than public education at large.

The latter result suggests that years of propaganda have had an effect: Republicans have successfully cast teachers’ unions as obstreperous, greedy forces bent on radicalizing children in the classroom. And to a certain degree, Democrats have bowed to that characterization. Michelle Rhee, a prominent Democratic proponent of education reform, reliably sounds like a Republican when it comes to teacher work stoppages. “It was frustrating to hear Chicago Teachers Union President Karen Lewis say toward the end of the dispute that the strike would continue to see whether there is ‘anything else they can get,’” she wrote in 2012. “But at least that was clear evidence that, for union leaders, this strike was never about what was best for kids.” Compare that to Republican Governor Matt Bevin, who said striking teachers in Kentucky were “selfish and short-sighted.”

At the state level, Democratic legislators have been complicit in tax cuts and reform programs that steadily stripped funds away from public schools. The spending cuts that eventually propelled teachers out of classrooms in West Virginia began under Democratic administrations, and it is nowhere near certain that teachers will fare better under a Democratic replacement for Governor Jim Justice. (Justice, recall, ran as a Democrat, and switched parties in office last year.)

In Oklahoma, Republican Governor Mary Fallin replaced a Democratic governor, Brad Henry. Henry signed massive tax cuts into law during his tenure, and he isn’t the only state Democrat culpable for stripping the state of needed funds. A 2016 study by the Oklahoma Policy Institute found that bipartisan cuts to state income tax cost the state $1 billion annually, with immediate consequences for public education. “Based on the budget proportions of the largest state agencies,” the study’s authors wrote, “that means without tax cuts Oklahoma could be investing $356 million more into K-12 education, enough to provide raises of about $6,000 per teacher or to combine teacher raises with additional days of instruction, reduced class sizes, and expanded priority programs such as early reading instruction.”

So who benefited from this bipartisan effort? Wealthy Oklahoman households, which shrank their tax bills at the expense of teacher bank accounts. And while the state cut taxes, it created school choice programs. The Lindsey Nicole Henry Scholarship, a program that provides school vouchers to children with certain disabilities, was passed by Henry, is named for Henry’s daughter, and costs the state millions every year.

In Kentucky, the funding crisis that plagues the state’s pension systems predates Bevin’s time as governor. Bevin, in fact, is only Kentucky’s second Republican governor since 1971: Democrats had plenty of time to shore up public education in the state and to fully fund pensions for public employees. The state’s ongoing misfortune indicts both parties; the practical consequences of their respective neglect and frequent hostility bear such similarity that they may as well be identical.

Liberal hopes that the strikes signal a forthcoming blue wave reinforce the Democratic Party’s uneven relationship with teachers and their unions. Unions don’t just exist to turn out votes for Democrats. Rather, unions safeguard the interests of teachers—and by extension, students—from the bipartisan forces that have hollowed out public education in this country. If Democrats truly support striking teachers, they should embrace public education on its own merits, along with worker rights. These two causes are linked in the resistance against Trump, as a defense of the public good against predatory private interests. Democrats would do well to remember that the teachers have always been here, before Trump and before the marches, and so have the troubles that drove them into the streets.