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It once seemed as if Democrats would never stop fighting the Hillary-Bernie wars. But deep into this primary season, those fears have not been borne out.

The era of “the resistance” has proven electorally and politically mobilizing for Democrats of all stripes.

We have seen insurgent victories in primaries by progressives and also successful campaigns by establishment-backed moderates. All the while, the substance of the party’s agenda continues to move leftward, with both left and centrist candidates standing behind Medicare-for-all, a $15 minimum wage, and tuition-free college.

Overall, recent intraparty struggles have redounded to progressives’ benefit even as the insurgent-outsider-storms-the-gates dynamic of the Bernie Sanders campaign has been left behind.

This is good news for the left, and history helps account for what we’re seeing. Sanders supporters and other like-minded progressives, many of them comfortable with the language of socialism and a hard-edged critique of American liberalism, typically portray themselves as a both a new and fundamentally external force in Democratic politics. Often, the media accepts this characterization.

But the Sanders wing of the Democratic Party manifestly belongs to a robust and consequential tradition of left-liberal activism within the party, one that stretches back to the middle of the 20th century and has long aimed at transforming the party into more of a vehicle for social democracy.

There are consequences for not knowing this history: If the left comes to see itself as existing entirely outside the Democratic Party, its proponents may experience cynicism and alienation when the going gets tough and they lose intra-party struggles.

If the party’s strongest progressive critics would embrace their homegrown Democratic lineage, rather than resisting it, they’d likely only be more effective in changing the party further.

The case the left makes against the Democrats

The progressive critique of contemporary Democratic politics that emerged during the Obama years and defined the Sanders campaign is diverse enough to risk overgeneralization. But several substantive, strategic, and tactical themes have recurred. And this critique, emphasizing both corruption and fecklessness, remains potent in left-of-center circles.

One line of criticism casts Democratic policymaking as a pro-corporate betrayal of the party’s egalitarian economic traditions. “From the late 1980s to 2016, neoliberal ideas held hegemonic sway among the Democratic elite,” argues the Week’s Ryan Cooper — thereby sapping the party’s electoral support.

The revival of party critiques grounded in political economy is epitomized by the success of the socialist Jacobin magazine, whose founder Bhaskar Sunkara argued years before the Sanders campaign that left-wing mobilization driven by a fundamental critique of capital would actually help the fortunes of more moderate welfare liberalism.

Dovetailing with the ideological argument is an electoral one claiming that the hunt for allegedly “moderate” swing voters is doomed to fail, and also undermines the attempt to build a strong (that is, left) party agenda. “We continue to run conservative Democrats and they lose,” the insurgent Nebraska congressional candidate Kara Eastman told the Nation’s editor Katrina vanden Heuvel.

Rather than “prioritizing the chase for elusive Republican voters,” according to a post-election “autopsy” underwritten by Action for a Progressive Future, the party should focus on mobilizing its own base, “especially people of color, young people, and working-class voters overall.”

Such a strategy demands specific tactics in campaigns, legislative fights, and debates in the public square. Writers like Sunkara insist that the development of policy ideas must be tethered to “a dynamic theory of power.” This means not only putting worker empowerment and institutions like unions at the center of a political agenda but also emulating Republicans who “bind themselves to an ideological code” and enforce discipline within their ranks. Indeed, calls to emulate the partisan discipline and ideological cohesion of Republicans abound in contemporary progressive commentary and advocacy.

As Cooper argues, the left “could learn a lot from the example of Barry Goldwater’s run for president in 1964,” which showcased the power of “disciplined organizing and dedication” to transform a major party from within.

There’s no reason such criticisms can’t come from within the Democratic Party. And historically they have.

Reading such arguments in recent years gave me déjà vu — and made me feel old. That’s because so much of it is reminiscent of the discourse among liberal pundits and netroots activists during the mid-2000s, a period when I worked as a journalist.

During the Bush era, we condemned Democrats for substantive incoherence and misguided pandering to a mythical center. And we looked to the modern right’s origin story, captured in works like Rick Perlstein’s Goldwater history Before the Storm, as a model for ideological revival within the Democratic Party.

The George W. Bush years saw a slew of liberal institution-building in media, advocacy, donor consortia, and policy development, an insurgent presidential candidacy championing “the Democratic wing of the Democratic Party,” and a notable shift toward both increased party discipline and a more ambitious national policy agenda.

As I explained in my book, The Polarizers: Postwar Architects of Our Partisan Era, such patterns of criticism and factional insurgency have, in fact, recurred in the Democratic Party since the New Deal. Democrats have long been the more coalitionally and ideologically diverse of the two major parties, but that has given liberal activists all the more incentive to build up factional power within the party and to push for reforms that would advantage them and their agenda.

At midcentury, the Democratic Party bestrode the country as an electoral colossus, but that reach came at the cost of ideological consistency: The party contained within its ranks not only a growing cohort of Northern liberals but also a powerful faction of racially and economically conservative Southerners. The latter, advantaged in Congress by the seniority system, worked with Republicans to bottle up legislative proposals for civil rights and labor reform.

Such efforts helped account for the era’s uniquely high levels of bipartisanship and low levels of party polarization, and it sparked an intellectual and political critique of bipartisanship by liberal activists, labor and civil rights advocates, and allied politicians. This coalition valorized party discipline in Congress and majority rule within the party, since liberals were becoming increasingly numerically predominant within its ranks.

So-called “amateur” Democratic activists battled with traditional machines over control of state and local Democratic organizations while seeking to disempower Southern Democrats in national party affairs. They also relentlessly criticized the likes of congressional leaders Sam Rayburn and Lyndon Johnson for reaching across the aisle.

Historian and political activist Arthur Schlesinger gave voice to these advocates in a 1955 strategy memo that blamed legislative cooperation with President Dwight D. Eisenhower for “squeezing a good deal of the vitality out of the Democratic appeal.” Democrats needed a counterstrategy to “clarify the differences between the parties,” he argued, in part by passing bills intended to draw presidential vetoes.

Substantively, postwar liberals advocated an extension and expansion of the New Deal project while emphasizing, unlike some earlier Democrats, the inextricable connection between an egalitarian economic agenda and a commitment to civil rights. Their intraparty advocacy and organizing helped produce the unprecedentedly liberal 1960 Democratic Party platform, an important predicate for the eventual passage of the 1964 Civil Rights Act, the 1965 Voting Rights Act, and Johnson’s Great Society agenda.

A subsequent generation of liberal and left-wing activists emerged from the social movement mobilizations of the 1960s. They mounted intraparty insurgencies through the antiwar presidential campaigns of Eugene McCarthy and Bobby Kennedy in 1968, as well as the subsequent push to reform the party’s nominating procedures and its operation in Congress.

These efforts carried forward the project of breaking down the transactional features of American parties and injecting greater ideological commitment into American politics. And they pushed the Democrats leftward.

In the later 1970s, as the right gathered strength nationally, progressive activists sought to build up new factional influence within the Democratic Party. Activists initially inspired by the era’s cultural politics recognized that they had to more effectively appeal to working-class constituencies and forged ties with labor activists around a cosmopolitan social democratic agenda.

The writer and activist Michael Harrington’s Democratic Socialist Organizing Committee pursued platform work at the Democratic convention in 1976 and the party’s midterm issues conference in 1978. That, in turn, laid the groundwork for Ted Kennedy’s ideologically charged 1980 nomination challenge to Jimmy Carter.

Even in the 1980s, when culturally moderate and business-friendly forces within the party formed the Democratic Leadership Council and gained significant factional power, left-liberals reaffirmed their coalitional and ideological hold on the Democratic base. Jesse Jackson’s potent and organizationally innovative presidential campaigns in 1984 and 1988, for example, championed a program of multiracial economic populism while drawing important new activists and operatives into Democratic politics.

The party’s moderate “New Democrat” wing reigned triumphant in the 1990s, embodied in Bill Clinton’s presidency. But Clinton’s righter-leaning pursuits hardly went unopposed by liberals occupying the party’s center of gravity. (Three of his most prominent centrist efforts — the North American Free Trade Agreement, fast-track executive authority to negotiate trade deals, and 1996’s welfare reform bill — were opposed by majorities of congressional Democrats.) And discontent with the Clintonian approach to policy and politics helped to lay the groundwork for the critiques that would be offered by progressives during the subsequent Bush years.

Though each wave of activism and insurgency within the Democratic Party has eventually crested and receded, the impact on the party’s makeup, agenda, and behavior has been cumulative — and powerful. Look at the party today: Staunch conservatives are now extinct within it.

Leaving Sanders supporters’ criticism of neoliberal sellouts to one side, a labor-liberal alliance committed to both economic and social liberalism remains the party’s center of gravity and ideological anchor. Hillary Clinton’s own campaign platform in 2016, thanks in no small part to Sanders’s challenge, exemplified this trajectory. It was substantially more liberal than not only her husband’s record in office but also her own campaign agenda in 2008.

During the last decades of the 20th century — adverse years for social democracy across the West — rumors of liberalism’s death within the party proved greatly, and repeatedly, exaggerated. And in the first two decades of the new century, across virtually every major issue, the party’s national agenda has moved steadily and significantly leftward, with no imminent signs of slowing down.

Why understanding this history matters for the left

Why is it important to recognize that today’s progressive brawlers have a rich and fruitful historical legacy inside the Democratic Party? Because those activists’ tendency to view the party as a monolithically hostile, alien force carries with it a major downside, which was all too painfully manifested in 2016: Useful critique and insurgent energy can curdle into cynical disaffection.

In their sense of disconnection from the Democratic Party, such activists reflect the times. Contemporary polarization is dominated by negative partisanship rather than positive partisan loyalties. American parties are increasingly hollow organizations that fail to command popular legitimacy.

It’s unsurprising that even sophisticated, historically informed left-wing analysts like Jacobin’s Seth Ackerman can conclude that “building a genuinely independent party rather than a mere informal faction of the Democrats” is necessary to achieve fundamental change. He comes to this conclusion despite being fully aware of how monumentally difficult such a task would be.

My read of Democratic history says otherwise. For all the frustrations and setbacks they’ve experienced in the process, the change that progressives have brought over time about by leveraging power within the party has been substantial and meaningful. Though the American two-party system really is formidable, and perhaps intractable, the saving grace for activists has long been that the two major parties are also highly permeable: It is abundantly possible for organized factions to infiltrate parties and alter their course.

Better understanding their intraparty history might incline progressives to be more effective factional actors — more attuned to what the key levers of influence are within the party and in the broader political system. It might also help them avoid undermining the party’s legitimacy or exacerbating popular alienation. For today’s disaffected left, there’s power in recognizing that it’s their party too.

Sam Rosenfeld is an assistant professor of political science at Colgate University and author of The Polarizers: Postwar Architects of Our Partisan Era.

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