Now a step away from the Republican nomination, Donald Trump is keener than ever to encourage his violent fans. “Knock the crap out of them,” he says. Statements like these, combined with Trump’s xenophobia, have led to debates about whether he is, in fact, a fascist. That historians of fascism are now being asked to weigh in indicates the gravity of the matter.

No matter how deep Trump’s fascist-ish tendencies seem to go, however, there are huge differences between today’s political context and that which gave rise to figures like Hitler and Mussolini. And America’s history is more illuminating than Europe’s if we’re trying to explain the Trump phenomenon.

Senate minority leader Harry Reid had one of the better reads on the situation. As he said on the Senate floor a few weeks back, “Republicans have spent the past eight years stoking the fires of resentment and hatred, building Trump piece by piece.” Still, it was more than racist rhetoric that created the American right’s Frankenstein monster.

Similarly, while Trump’s popularity is in part attributable to his regular use of right-populist tropes — a strategy deployed with great success in Europe as well — even more important is that there’s an audience already primed for his message. The infrastructure that paved Trump’s road to electoral success was built largely by the Tea Party, an umbrella term for the web of organizations that radically restructured the Republican Party following the 2008 election and financial crisis.

The Tea Party began, after all, with one of Trump’s favorite jabs. Speaking from the floor of the Chicago Mercantile Exchange just weeks after President Obama’s inauguration, CNBC Squawk Box correspondent Rich Santelli chided the president for “subsidiz[ing] the losers’ mortgages,” sparking cheers from the stockbrokers surrounding him — a group he described as a “pretty good statistical cross-section of America; the silent majority.” Santelli made sure to build a well-placed call to action into his rant: “We’re thinking of having a Chicago Tea Party in July. All you capitalists that want to show up to Lake Michigan, I’m going to start organizing.”

Santelli didn’t represent a “silent majority,” but he wasn’t alone. As sociologists Theda Skocpol and Vanessa Williamson have documented, Tea Parties spread rapidly. Less than ten days after Santelli’s tirade, dozens of modest protests were held around the country, swelling through April to include more than three hundred thousand people.

By the following spring, the Tea Party had already begun effecting major shifts in state governments, beating established GOP candidates in several Republican primaries. That November, spurred on by anger at Obamacare, Tea Party–linked candidates won 39 of 129 House races and 5 of the 9 Senate races they contested.

Skocpol and Williamson argue that the Tea Party gained momentum through a complex relationship between top-down and bottom-up forces. The cheerleading from conservative outlets like Fox News and backing from established think tanks and nonprofits such as Americans for Prosperity — which deployed paid organizers to seventeen states between 2005 and 2009 — helped the fledgling movement immensely.

But just as central were genuinely grassroots outpourings of support for Tea Party positions, which found expression in some nine hundred local chapters. “Local Tea Party groups,” Skocpol wrote recently in Dissent, “met in churches, libraries, and restaurants, and collected small contributions or sold books, pins, bumper stickers and other paraphernalia on commission to cover the modest costs,” often trumpeting views divergent from the Kochs and other big-money donors.

While tricornered hats and a set of shared conservative values made the party look coherent to the media, they were never a uniform set of Heritage Foundation free marketeers. Hostile to Obama and weary of both taxes and terrorism, Tea Partiers — generally older, white, and with histories of conservative activism — nevertheless defended the government programs they benefited from, such as Social Security and Medicare.

The Tea Party’s grassroots zeal has since waned, but they succeeded in remaking the Republican establishment and Congress in their image. “What used to be the Tea Party,” Skocpol told a Bloomberg reporter in November, “is now the GOP.” Activists have channeled once-fringe views, peddled in church basements and town hall meetings, into the highest levels of government.

Today, the Tea Party base is Trump’s base. The voters the movement activated are partial to candidates that buck the establishment, and thus extremely receptive to the billionaire’s appeals.

Ironically, that establishment now includes Ted Cruz, the former Tea Party rising star and Trump’s top challenger. A late February poll by CNN found that just 16 percent of Tea Partiers lean toward the Texas senator. Fifty-six percent favor Trump, who maintains sizable margins among the same voters in several states. Yet while the Tea Party’s grassroots base has spurned Cruz, its elites are scrambling to dump Trump.

Top Tea Party donors have been relatively open about their criticisms of Trump. Club for Growth Action, a PAC known for supporting Cruz and other Tea Party candidates, has spent $6.2 million against him. While the Koch network has yet to issue a formal attack, its chief political operative left his job to go advise Marco Rubio’s campaign before it folded. And the Koch-tied American Future Fund has spent $4 million on anti-Trump efforts. The group’s highbrow orthodoxy chafes at Trump’s attitudinal populism, marked more by an antipathy to establishment conventions than an embrace of market dogmas.

Railing against the “bad deals” that have driven American jobs overseas and Rust Belt economies south, Trump has endeared himself more to poor white voters than Koch-funded politicians ever could, and expanded the Republican base on the strength of Tea Party support. Some twenty thousand Massachusetts Democrats, for instance, added their names to the GOP rolls in advance of Super Tuesday.

Three-fourths of Tea Partiers and two-thirds of Republicans believe that life in America has gotten worse since the 1950s. And working- and middle-class whites’ lives have gotten worse since the recession. With no alternative left vision, populist-tinged Tea Party nativism swooped in with a seductive narrative and a ready-made platform of disaffection.

Promising to “Make America Great Again,” Trump is now selling older Tea Partiers’ anxious nostalgia to generations too young to remember (white) postwar prosperity. He’s a right-wing tribune for disillusioned white men, young and old, marshaling racist tropes long thought politically taboo in their defense.

Though more ambivalent about the role of government than many Tea Party leaders, Trump draws from the same rhetorical well. “They’re taking our manufacturing jobs,” Trump says of Mexican immigrants. “They’re taking our money. They’re killing us.” The solution, he insists, is to hand him the reins.

And most Tea Parties would be happy to do just that. They are the candidate the base of the movement has been waiting for. Disrupting the elite-grassroots nexus that Skocpol and Williamson credit with powering the Tea Party’s initial rise, Trump has given birth to a more resilient, more virulent strain of far-right politics.

It may be some consolation that Trump’s rise is the result of eight years of skilled political handiwork — not some innate brutality in the American electorate. Skocpol calls him “a great entertainer . . . able to take advantage of a number of dynamics in American politics as they exist right now.”

Indeed, the Left might even be able to learn from Trump’s ascent.

Today’s crisis of legitimacy presents the perfect opportunity to use time-honored tools of grassroots organizing to buck Democratic Party elites and build an inclusive left politics, both within and beyond the Sanders campaign. While Trump thrives on cobbling together a political identity of the past, the Left can build a politics for the future. No center-left nostrums, no racially coded reminiscence — just a bottom-up program of redistribution and antiracism.