Pablo Martinez Monsivais / Pool via Reuters

Representative John Lewis had just finished delivering a heartfelt tribute to the retiring Republican Senator Johnny Isakson on the House floor last month when he looked over to his ailing fellow Georgian. “I will come over to meet you, brother,” Lewis told him as he laid his remarks down on the rostrum.

The two aging politicians each walked gingerly toward the center aisle of the chamber and met in a bipartisan embrace. Lewis, the civil-rights icon and widely acknowledged “conscience of the Congress,” had bestowed a measure of his seemingly limitless supply of grace on an old friend, who had announced that he would soon be resigning due to the mounting effects of Parkinson’s disease.

Now, not even six weeks later, it is the 79-year-old Lewis who must ask for the nation’s prayers. The longtime Democratic congressman disclosed last night that he had received the grimmest of diagnoses: Stage 4 pancreatic cancer. Though he said he was “clear-eyed” about the prognosis, Lewis vowed to fight the disease and continue serving in the House while he undergoes treatment. Still, the news forced members of both parties to contemplate the possibility—perhaps, unfortunately, the likelihood—of an earlier-than-expected departure from the Capitol of a man who has become, perhaps, the last truly unifying force in national politics.

Tributes and well-wishes quickly poured in from all corners, just as they did in 2017 and 2008, when Senators John McCain of Arizona and Ted Kennedy of Massachusetts, respectively, revealed their similarly bleak cancer diagnoses. Former President Barack Obama praised Lewis’s “incomparable will to fight,” while the top Republican in the House, Minority Leader Kevin McCarthy, lauded him as a patriot, a civil-rights icon, and “a friend first and foremost.” “They don’t make them stronger or braver,” Isakson said, returning the accolades Lewis had given him weeks earlier.

Nearly all the statements alluded in some oblique way to the moment that forged Lewis’s lifelong reputation for courage and moral rigor: During a 1965 march across the Edmund Pettus Bridge, in Selma, Alabama, a state trooper beat Lewis, then 25, so badly that he fractured his skull. It was not the first time that Lewis, the chairman of the Student Nonviolent Coordinating Committee and the youngest speaker at the 1963 March on Washington, was injured while demonstrating for civil rights. He has repeatedly returned to Selma on the anniversary of “Bloody Sunday,” bringing a bipartisan delegation of congressional leaders to lock arms in symbolic unity as they cross the Pettus Bridge before a crush of media.

Lewis’s civil-rights background has conferred on him a moral authority unique among the 535 members of the House and the Senate. He speaks frequently of the “good trouble” he caused in the 1960s and in political fights since. And in the thundering speeches he occasionally delivers on the House floor, Lewis invokes the language of moral courage. Most recently, that was during the impeachment of President Donald Trump. “For some, this vote may be hard, but we have a mission and a mandate to be on the right side of history,” Lewis said in explaining his support for the articles of impeachment.

The announcement of Lewis’s illness is an even sharper hit to Congress as it comes just two months after the unexpected death of Representative Elijah Cummings of Maryland, another veteran House Democrat deeply respected by members of both parties. (The two bald-headed African Americans were so often mistaken for each other by newcomers to the Capitol that Lewis used this past April Fool’s Day to announce that he was growing a beard to help people distinguish them.)

Yet, as with his ally Martin Luther King Jr., Lewis’s current image as a unifier and moral beacon tends to sanitize his career, overlooking the violent opposition he encountered during the civil-rights movement, the confrontational protest tactics he used to effect change, and his then-radical policies. Lewis’s political career has also been more complicated, and interesting, than is widely understood. He lost his first bid for Congress, in 1977, and then won in an upset victory in 1986 over a friend turned rival, Julian Bond, a fellow veteran of the civil-rights movement who was then better known nationally. The race was bitter and divisive, with Lewis at one point challenging Bond to take a drug test.

Although Obama and Lewis became close friends and allies, the congressman was late to see the potential of the man who would become the nation’s first black president. Lewis endorsed Hillary Clinton for the Democratic nomination in October 2007, before switching his support to Obama four months later, only after the senator from Illinois had demonstrated his strength among white and black voters alike by winning primaries across the country.

In January 2017, Lewis’s decision to boycott Trump’s inauguration sent the president-elect into one of his early presidential fits of rage. Lewis was not the first Democrat to declare that he was skipping the ceremony, but he was the most prominent, and after Trump lashed out at him, dozens of Democrats joined the boycott. (Lewis also missed George W. Bush’s first inauguration, as a form of dissent against the Supreme Court’s ruling to end the recounts in Florida.)

Still, like so many of his prominent colleagues in Congress, Lewis never turned into a partisan figure. In many ways, his trajectory over the decades has been the opposite of that of America at large: As politics have become ever more tribal and polarizing, Lewis’s image has softened and grown more broadly appealing to politicians seeking even just one example of a moral leader who can transcend the ideological divide. In recent years, Lewis would receive one or two votes for House speaker from more conservative Democrats seeking a less contentious option than Nancy Pelosi. Yet Lewis is no centrist: He’s a liberal Democrat, and like McCain and Kennedy before him, he is revered more for his willingness to befriend and engage members of the other party than for his tendency to vote with them.

While none of them, together or individually, was able to steer Congress off its path toward more division and gridlock, there remains the fear of another incalculable loss whenever Lewis leaves the Capitol, whether through retirement or illness. Without Lewis around, will there be anyone left in Congress to fill that unifying void?

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