In his youth, long before he became a civil rights icon—a phrase invoked in recent days by the Associated Press, Wall Street Journal, NPR and countless other news outlets—Lewis stood firmly in the American radical tradition. No less strident in his condemnation of American hypocrisy than Frederick Douglass or W.E.B DuBois before him, he shined a spotlight on systemic injustice. He deployed nonviolence with an implicit understanding that it would generate social and economic disturbance and compel civic and business leaders to bend to the movement’s demands. He was the scourge of liberals inside the Kennedy administration, conservatives on the editorial board of the National Review and centrists who counseled moderation and patience. In short, his role was to make Americans profoundly uncomfortable.

But radicalism is only one half of Lewis’ legacy. The other half is how Lewis, along with other movement activists who later held elective office—Andrew Young, Marion Barry, James Clyburn, Julian Bond, to name just a few—took his radicalism inside the establishment, forever changing the character of the Democratic Party and, with it, the political direction of America itself. They made civil rights an unnegotiable strain of the party’s DNA and built Black-led political organizations of a sort unknown since the heyday of Reconstruction.

One might well ask if electoral politics tamed the radicalism of movement leaders like Lewis. But the more important question is how those leaders transformed partisan politics and gave birth to a new Democratic Party positioned for long-term success in a diverse 21st-century America.

Raised in rural Alabama, John Lewis knew early on that he was no farmer. He couldn’t stand the butchering of animals, had no love of manual work and instead aspired to the pulpit. At church, he would absorb the pastor’s sermon and then reimagine it at home, preaching to—and sometimes baptizing—the chickens on his parents’ property. He was the first in his family to graduate from high school, and though he hoped to attend Atlanta’s Morehouse College—a dream planted in his head after he heard a recording of Morehouse graduate Martin Luther King delivering a radio sermon titled “Paul’s Letter to the American Christians,” months before King achieved fame as leader of the Montgomery Bus Boycott—his family’s limited economic means consigned him to the American Baptist Theological Seminary in Nashville, Tennessee. There, Lewis fell under the spell of James Lawson, a brilliant seminarian who led workshops in nonviolent resistance. Along with fellow students Diane Nash, James Bevel, Bernard Lafayette and C.T. Vivian (who passed away the same day as Lewis, at the age of 95), he became a leader of the lunch-counter sit-in movement that exploded across the South in 1960. The rest, as they say, is history.

John Lewis was seemingly everywhere in the early 1960s. He was a founding member of the Student Non-Violent Coordinating Committee in 1960. A year later, he was among the first dozen Freedom Riders who set out from Washington, D.C., to test the Interstate Commerce Commission’s ban on segregated accommodations at interstate bus terminals. On that journey, he was savagely beaten in Rock Hill, South Carolina, and Montgomery, Alabama.

It’s indisputable that Lewis and other activists changed many a heart and mind through their promise of peace and reconciliation. But moral suasion went only so far. In May 1961, 57 percent of respondents to a Gallup poll answered that “‘sit-ins’ at lunch counters, ‘freedom buses,’ and other demonstrations by Negroes” would hurt the civil rights cause (that figure rose to 74 percent by the spring of 1964); only 28 percent thought they would help. The same poll found that 22 percent of respondents approved of Freedom Rides, while 61 percent disapproved. Even as they sought to build a beloved community that spanned all races and creeds, Lewis and his colleagues offered Americans a blunter, if implicit, promise: discomfort, even chaos, until their demands were met.

In 1963, as chairman of SNCC, he spoke at the March on Washington, delivering an address that was originally so strident that movement elders compelled him to water it down. That first draft, which Lewis never delivered, held that “if any radical social, political and economic changes are to take place in our society, the people, the masses must bring them about,” and included a pledge to “march through the South, through the heart of Dixie, the way Sherman did. We shall pursue our own ‘scorched earth’ policy and burn Jim Crow to the ground—nonviolently.”

On the steps of the Lincoln Memorial, Lewis did not deliver those words. At the insistence of nearly everyone senior to him in age—Martin Luther King, A. Philip Randolph, labor leader Walter Reuther, Catholic Archbishop Patrick O’Boyle, NAACP chief Roy Wilkins—he struck a slightly more conciliatory tone. But even the revision, which Lewis and other student leaders swallowed with deep regret, wasn’t exactly designed to make moderates comfortable. “Get in and stay in the streets of every city, every village and hamlet of this nation until true freedom comes, until the revolution of 1776 is complete. We must get in this revolution and complete the revolution,” Lewis told the demonstrators. “If we do not get meaningful legislation out of this Congress, the time will come when we will not confine our marching to Washington. We will march through the South … with the spirit of love and with the spirit of dignity that we have shown here today. By the force of our demands, our determination, and our numbers, we shall splinter the segregated South into a thousand pieces and put them together in the image of God and democracy.”

The popular narrative holds that many white Americans outside the South responded positively to the civil rights movement in the early 1960s, when it was a matter of peaceful protesters demanding things that didn’t directly threaten white families—the right to vote, the right to eat in a restaurant or take in a movie at the local theater— and that only when the movement turned to residential and school integration in the North, and when cities erupted in urban rioting after 1964, did “backlash” occur. In 1966, Harry McPherson, a top aide to President Lyndon B. Johnson, sat down for an off-the-record conversation with Robert Novak, one of the country’s leading political columnists. “We mostly talked about civil rights,” McPherson reported to his White House colleagues. “He is convinced that the white backlash is growing as a response to the riots and the fair housing legislation. … He said that negative reactions were spreading to the white middle class from the white lower class and this presented the gravest danger to progress the civil rights movement has yet faced.”

This wasn’t exactly right. McPherson knew all too well that backlash had been in evidence long before the movement grew more strident, and well before urban centers went up in flames. Much in the same way that today’s Black Lives Matter protesters are damned if they take a knee and damned if they take to the streets, Gallup found in 1963 that 60 percent of respondents opposed the March on Washington, an event now revered as a crowning moment in America’s political development. It wasn’t just the text of Lewis’ speech—original or revised—that was bound to make people uncomfortable. It was the event itself.

The following year, Alabama’s segregationist Governor George Wallace, won 25 percent of the Democratic presidential primary vote in Wisconsin and 30 percent in Maryland. Campaigning in Milwaukee, where more than 700 white men and women packed the local Serb Memorial Hall, Wallace railed against the civil rights bill then still pending in Congress, promising that it would imperil their jobs, neighborhoods and safety. “A vote for this little governor will let people in Washington know that we want them to leave our houses, schools, jobs, businesses and farms alone,” he roared to thunderous applause.

It wasn’t just racial conservatives who found the movement threatening or inconvenient. SNCC’s tactics drove liberals inside John F. Kennedy’s White House to distraction. Acutely sensitive to the Cold War politics at play—how, after all, could America vie with the Soviets for the allegiance of so many decolonized nations in Asia and Africa, when Jim Crow violence was fully on display at home?—Kennedy’s administration regarded the Freedom Rides and desegregation marches as deeply embarrassing. In 1961, Lewis spent 37 days in Mississippi’s infamous Parchman Penitentiary, not because the Kennedy Justice Department failed to intervene on the Freedom Riders’ behalf, but because the Kennedys, seeking to avoid a repeat of the violence that had erupted in Alabama—where rioters blew up a Greyhound bus, and where Lewis and other Freedom Riders were savagely beaten as police officers stood passively by—explicitly arranged with the governor to have the passengers quietly arrested and escorted to prison upon their arrival at the Trailways bus station in Jackson.

The evening after he signed the Civil Rights Act of 1964 into law, Johnson famously told his aide, Bill Moyers: “I think we just delivered the South to the Republican Party for a long time to come.” Though the South took several decades to turn deep red, LBJ was right in one sense: That fall was the last presidential election in which the Democratic nominee took a majority of the white vote.

But people too seldom pause to reflect on the other side of the coin. Even as the Democratic Party lost its hold on white voters and began to cede the once-solid South to a more conservative Republican Party, the Voting Rights Act of 1965 brought millions of Black Southerners into the electorate and, almost instantaneously, the Democratic Party. Going forward, support for civil rights would become a sine qua non for Democrats from the presidential level all the way down to local municipal races. In the South, Democrats like Edgar Mouton, a Louisiana state senator who marveled at never having “shook hands with a Black person before I ran for office,” would now have to visit Black neighborhoods and churches and ask Black voters for their support. The result was a rising generation of “New South” governors, like Bill Clinton of Arkansas, Ruben Askew of Florida and Jimmy Carter of Georgia, who brought African Americans into state government and built more inclusive state parties.

At the same time, a rising generation of Black political activists, including Lewis, cut their teeth in the 1960s and 1970s as staff members for various initiatives funded by or associated with the Great Society, and later went on to run for office.

In 1977, a nationwide survey of Black mayors, city council members and state representatives found that 20 percent had been involved with community action programs in the prior decade, while many others worked or volunteered with a broader range of Great Society initiatives. Lewis’ trajectory—from civil rights leader to community organizer to the Atlanta City Council and then to Congress—was in many ways typical of this journey. In effect, the civil rights movement ported its radicalism into the Democratic Party and used politics as a base to build more permanent political power for Black Americans on school boards, in statehouses and city halls and in Congress.

There was little in Lewis’ background that naturally suggested a career in politics, though that might have been said of most civil rights soldiers. A year before he first became a public figure as a leader of the Nashville movement, Lewis attended a workshop at the Highlander Folks School, an Old Left training ground for labor, peace and civil rights activists. There, a visiting professor deemed him poor fodder as a leader. He spoke haltingly, he stuttered, he struggled to read texts aloud. “What difference does that make?” retorted Septima Clark, the legendary Black educator who was also there that week. Lewis possessed an inner calm and a deep understanding of ideas—the Social Gospel, Gandhian principles, democratic theory. She saw in him something greater than his unpolished exterior. The civil rights movement impressed on Lewis and many of his compatriots the idea that politics is the most powerful vehicle of change. Once he adopted that belief, he never looked back.

Today, as a rising generation of activists take to the streets—literally pursuing a “scorched earth policy” in some cases, by toppling the statues of Confederate heroes—Lewis and his generation offer a road map. Before he was widely cherished as the elder statesman of a popular movement, Lewis helped effect change in a nation resistant to upending its long-standing racial order, and then brought his radical brand of politics into the political system itself.

Sixty years after he first burst onto the scene, it’s fitting that Lewis has left us in a moment when a new generation has inherited his essential radicalism. No less now than then, “good trouble” doesn’t make everyone feel comfortable. Nor should it. Good trouble begins as trouble. Only later does it seem safe.

Joshua Zeitz, a Politico Magazine contributing editor, is the author of Building the Great Society: Inside Lyndon Johnson's White House. Follow him @joshuamzeitz.