Sen. Bernie Sanders held court in Iowa earlier this month. (Charles Ommanney/The Washington Post)

Whenever Sen. Bernie Sanders talks about overthrowing the system — his campaign “is nothing short of the beginning of a political revolution,” he declared in his New Hampshire victory speech Tuesday night, for instance — mainstream Democrats roll their eyes. Frankly, you can’t really blame them: They’ve heard this talk before, and it never ends well. Howard Dean in 2004 and Jesse Jackson twice in the 1980s used similar rhetoric to briefly exhilarate, then bitterly polarize, the party before their campaigns imploded. George McGovern promised to harness the left wing’s youthful energy; his dismal landslide defeat by President Richard Nixon in 1972 continues to haunt the Democratic establishment, which now seeks to filter presidential candidates through one paramount criterion: electability.

In the name of electability, Sanders’s liberal critics dismiss him as naive. Hillary Clinton, who calls herself the “practical” one, condescendingly rebuffs his ideas as “good on paper” but irrelevant to what Democrats need: “a progressive who likes to get things done.” Her constant pleas to “get back to the middle” and reclaim “the big center” place her in the pragmatic liberal tradition of presidents Franklin Roosevelt, Harry Truman, Lyndon Johnson and her husband, Bill — while distancing her from the ideologues of her party’s past. She and her supporters echo Christopher Lasch’s fatalistic lament that “radicalism in the United States has no great triumphs to record” and imply that it does more harm than good.

But in so doing, they forget an important lesson from Democratic history: Today’s consensus liberals cribbed most of their ideas from yesterday’s contrarian revolutionaries. In politics, as in nature, all motion is relative, and the political center that Clinton and her allies claim was, not long ago, considered the fringe. American liberalism’s greatest achievements to date — progressive reforms, the New Deal, the Great Society, feminism and multiculturalism — were all born from revolutionary movements. And many goals that once appeared unachievable (for instance, a progressive income tax or same-sex marriage) eventually became inseparable from the Democratic platform. The mainstream liberal order Democrats want to protect would never have come about without the revolutionary talk they now deride.

Some of the earliest organized challenges to the dire social, economic and political consequences of industrial capitalism in the late 19th century originated with the disgruntled agrarian forces of the Midwest and South. These revolutionary tides mobilized the Populist movement and eventually led to the short-lived People’s Party, a national organization with radical economic and political ideas but reactionary cultural ones (including xenophobia, anti-Semitism and anti-intellectualism). At their formative convention in Omaha in 1892, party officials issued demands that came to be known as the Omaha Platform. “We seek to restore the government of the Republic to the hands of ‘the plain people,’ ” it stated. At that time, according to Populist movement historian Lawrence Goodwyn, “millions of people” thought that “a wholesale overhauling of their society was going to happen in their lifetimes. A democratic ‘new day’ was coming to America.” Conventioneers adopted the Omaha Platform, calling for, among other things, a graduated income tax, an eight-hour workday, a “safe, sound and flexible” national currency, secret ballots, the introduction of ballot initiatives and referendums, the direct election of senators (rather than through state legislatures) and government ownership of the railroads.

The opposition was fierce: A plutocratic alliance of Northeastern financiers, railroad corporations and their political allies in both parties painted the Populists as dangerously radical. The New York Times called part of their plan “one of the wildest and most fantastic projects ever seriously proposed by sober man,” while an influential Nebraska newspaper labeled their leaders “shiftless, lazy and improvident” and grumbled that “it is a sin and a shame that these pests are permitted to beslime the state.” Mounting criticism of the Midwest-based movement led the influential newspaper editor William Allen White to famously first pose the question: “What’s the matter with Kansas?”

Within a few years, the answer was clear: nothing at all. Aside from proposals to nationalize the railroads, most of the original agenda of the People’s Party found its way into the Democratic Party platform. In 1896, the parties even temporarily merged as William Jennings Bryan became both the Democratic and the People’s presidential nominee. Within two decades, many of the Populists’ goals had been realized, if only partially, by Woodrow Wilson’s administration: The 16th Amendment and subsequent revenue acts of 1913 and 1916 ensured a graduated income tax, the 17th Amendment secured direct elections for senators and the 19th Amendment guaranteed women’s suffrage (another early Populist cause, especially in the West). In addition, the Federal Reserve Act of 1913 began to meet farmers’ basic need for a sound monetary supply. And while the Sherman and Clayton antitrust acts may not have dismantled the railroad cartels, the resulting regulations weakened their control of the economy, answering the complaint that had helped spark the Populist revolt in the first place.

If the costs of economic modernization challenged the intellectual and moral foundations of the modern Democratic Party, revolutionary shifts in the political consciousness of Americans prompted them to demand help from their government. In the wake of the Great Depression, the inevitable result was the New Deal, generally celebrated today as the epitome of common-sense liberalism. At the time, it was anything but.

In the 1930s and 1940s, labor unions, farmers, populists, progressives, consumers, technocrats and even socialists agitated for programs that eventually made up the enormous government undertaking. Gargantuan federal infrastructure projects included public ownership and planning (the Tennessee Valley Authority), government-funded mass employment (the Works Progress Administration), the regulation of labor-management relations and consolidation of collective-bargaining rights (the National Labor Relations Act) and the compulsory use of payroll taxes to fund retirement pensions (Social Security).

Even if they never conceded this in public, many New Dealers determinedly incorporated revolutionary proposals into their programs; Roosevelt privately admitted that “what we were doing in this country were some of the things that were being done in Russia.” When Huey Long, the governor turned senator from Louisiana, launched his “Share Our Wealth” campaign in 1934 to radically redistribute assets (possibly in the hopes of mounting a third-party challenge to Roosevelt), the president fired back with a redistributive plan of his own: Although the Wealth Tax Act of 1935 — also known as the “soak the rich” tax — was mostly a symbolic gesture that raised the income tax rate to 75 percent for only a handful of top earners, Roosevelt observed that it allowed him to “steal Huey’s thunder” and outflank him from the left.

Roosevelt’s detractors, even those from his own party, were horrified by these developments. The American Liberty League, for instance, was formed in response as an umbrella group for corporate executives and industrialists (such as the du Ponts). It was helmed by notable Democratic figures including former presidential nominees Al Smith and John W. Davis and the corporate executive John Jacob Raskob, who had served as chairman of the Democratic National Committee. “Just get the platform of the Democratic Party and get the platform of the Socialist Party, and lay them down on your dining room table, side by side,” Smith, a former New York governor, groused in a famous address at the league’s annual banquet in 1936. “Get a heavy lead pencil and scratch out the word ‘Democrat,’ and scratch out the word ‘Socialist,’ and let the two platforms lay there.” Claiming the mantle of Jefferson and Jackson as his own, Smith compared New Dealers to Marx and Lenin; he warned that “there can be only one capital — Washington or Moscow.”

Still, Roosevelt was undaunted. In his 1944 State of the Union address — part of which he called a “second Bill of Rights” — he invoked the founders’ spirit and asked Congress to establish the right to “useful and remunerative” employment; a regular paycheck that provides “adequate food and clothing and recreation” and ensures “a decent living”; adequate housing, education and medical care; and “protection from the economic fears of old age, sickness, accident and unemployment.” Today, most conservatives accept that the government is responsible for some public welfare, universal education, Social Security and even some job creation and health care.

The next generation of reformers wanted to go much further. If there ever was a genuine threat of revolution in America, it came during the late 1960s as an answer to the war in Vietnam. The New Left movement consciously brought the war home in an effort to end it: Mass demonstrations and protest marches by what Norman Mailer colorfully called “the Armies of the Night” paralyzed the nation’s major cities; acrimony between students and administrators bred clashes across campuses and transformed Kent State, Columbia and Berkeley (among others) into militarized battlefields; even the 1968 Democratic National Convention in Chicago degenerated on live television into a heartbreaking orgy of wrath, violence and hate. No wonder Nixon’s attorney general, John Mitchell, watching the antiwar protesters outside his office window, recalled the storming of the Winter Palace by the Bolsheviks.

To many protesters, the war was a symptom of what Paul Potter, the president of Students for a Democratic Society, called a “deeper malaise” plaguing America: Corporate capitalism was stifling the creative spirit and dehumanizing workers, faceless bureaucracies had colonized the democratic process, social conformity was rampant in a materialist consumer culture, institutional racism went unchecked, and strict patriarchal gender roles repressed women’s empowerment and individual sexuality. The activists, under the umbrella of organizations such as SDS, embraced diversity, integration, self-expression and personal autonomy (alongside more traditional economic concerns). They emphasized, as the Democratic Party’s revolutionary platform read in 1972, “the right to be different, to maintain a cultural or ethnic heritage or lifestyle, without being forced into a compelled homogeneity.”

The revolution to overthrow those anachronistic practices seemed dead on arrival: The disintegration of the New Left and McGovern’s disastrous presidential campaign heralded failure. Nixon won, then won again with the help of his “silent majority,” which delivered 12 more years of Republican rule after a one-term flirtation with Jimmy Carter. Decades later, the campaign finance system still inhibits genuine participatory democracy; the exhaustion of Keynesian policies in the 1970s allowed corporate capitalism to persist; Reaganomics and neoliberalism took hold.

But the uprising and its goals were not forgotten or abandoned: The insurgents eventually won the cultural war. They ushered in a “rights revolution” that set the stage for multiculturalism and the elevation of race, gender and sexuality on the Democratic Party’s national agenda — where they remain to this day.

Even Bill Clinton’s presidency, which in some ways seemed like an attempt to disavow liberalism’s revolutionary excesses, helped advance the cause. Yes, under his administration, guided by the moderate Democratic Leadership Council, Wall Street was increasingly deregulated (with the repeal of the Glass-Steagall Act in the late 1990s); income inequality skyrocketed despite the prosperous economy; and NAFTA solidified America’s embrace of neoliberalism. But Clinton also gave a greater voice than any of his predecessors to the issues of racial and gender equality, cultural diversity and universal tolerance — all causes of the New Left. He promised voters a Cabinet that “looks like America,” and he kept his word, assembling the most diverse administration to date and placing unprecedented numbers of women and minorities in Cabinet and government posts.

The “first black president” worked to compensate African American farmers for the billions of dollars they lost because of the government’s discriminatory farm loan program. Clinton’s National Homeownership Strategy helped lift minorities’ home ownership rates by about five percentage points (well above the average increase nationwide) and aided more than 2 million African Americans and Hispanics in acquiring their own homes. In addition, he contributed to their social mobility by raising the minimum wage by more than 20 percent. Clinton also pushed to expand reproductive rights, maternity leave and equal pay for women, despite the hypocrisy and sexism inherent in his affair with his intern. Although Clinton signed the Defense of Marriage Act in 1996, he also enacted “don’t ask, don’t tell,” a critical (if problematic) step toward integrating gay service members into the military.

In an important 2002 study, Ruy Teixeira and John Judis predicted an “Emerging Democratic Majority” that would result from the political realignment of minorities and working women, who began to coalesce around the party in the 1972 elections and gradually helped Democrats compensate for the defection of white working-class voters. For them, this shift constituted “George McGovern’s Revenge.” But it was also proof of just how powerful and pervasive the revolutionary sensibilities of the New Left proved to be. The coalition behind those ideas brought Barack Obama to power in 2008.

Like many of his predecessors, Obama employed revolutionary language on behalf of policies that, in retrospect, weren’t revolutionary anymore. A good example is Obamacare, rooted in Roosevelt’s insistence that every American had a right to adequate medical care. That notion had failed to animate Congress, despite the ardent support of Truman (who proposed a revolutionary national insurance plan), Johnson (who implemented part of that plan with Medicare and Medicaid) and first lady Hillary Clinton. Obama took a radical idea and achieved it in the least revolutionary way: winning an election, garnering congressional support for a somewhat curtailed program that dumped the public option and then barely getting the Supreme Court’s approval.

All these revolutionary ideas took hold inside the Democratic Party because their proponents shared something moderates lacked: a political imagination that looked beyond the status quo and imagined a different society. Those futurists were most successful during harrowing moments of national crisis. The Populists voiced the disgust of millions of Americans with the social ravages of industrial capitalism, in which the “Bourbon” Democratic establishment led by President Grover Cleveland was often complicit. Decades later, Roosevelt answered the Great Depression with New Deal ideas (economic nationalization and regulation, public ownership and planning, worker solidarity, and social welfare) conceived to prevent future depressions. The New Left modeled our multicultural future because its activists — unlike the moderate LBJ wing of the party, which was mostly satisfied with the civil rights legislation — were the only ones who even acknowledged there were still problems with racial, gender and sexual relations.

Revolutionary ideas still had to pass muster with electoral majorities, and it’s telling that several — the redistribution of taxes, the direct election of senators, women’s suffrage — even became constitutional amendments, which required overwhelming majorities in Congress and in state legislatures. The Supreme Court initially invalidated some of the New Deal’s most ambitious proposals (industrial- and agricultural-support laws), forcing Roosevelt’s allies to alter them without necessarily giving them up.

It’s fair for Democrats to press Sanders on how, exactly, he intends to achieve his “political revolution.” What is unfair is to dismiss his policies outright because they seem too far from the mainstream. Concepts from the left fringe have, throughout American history, served as corrective rather than destructive devices. Instead of smashing institutions, these ideas have mostly provided a moral compass for repairing them; many radical-worker, populist, progressive and even socialist ideas didn’t necessarily undermine the mainstream Democratic agenda as much as reorient it toward more urgent and just directions. Sanders’s push to fix a rigged economy and curtail campaign cash may shape the future Democratic agenda, regardless of whether he gets the nomination. (Clinton’s attempt to brandish her anti-Wall Street credentials shows that this shift has already begun.)

There is little doubt that Clinton’s pragmatic sensibility is invaluable for getting things done. But the revolutionary tradition in which Sanders stands can make sure they get done for the right reasons. In this way, the center and the fringe are symbiotic. Ideology is a terrible tool for governing but a necessary reminder of what government is for. Next time Sanders talks about revolution, skeptical mainstream liberals should hold their tongues and recall that the most exceptional quality of the American political system is its ability to absorb and implement so many revolutionary ideas without ever having had an actual revolution.

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