Last Saturday, dozens of former aides, friends, supporters and dignitaries gathered at the former synagogue that houses the Rainbow PUSH Coalition’s headquarters on the South Side of Chicago to commemorate the Rev. Jesse Jackson’s second presidential campaign 35 years ago. The organization’s founder, once a college football star towering at over six feet with broad shoulders, is now wheeled around by a group of trusted aides. Parkinson’s disease has ravaged Mr. Jackson’s body and arrested his speech — though according to those around him, it hasn’t slowed his mind.

Fifty-two years ago at the age of 30, Mr. Jackson broke away from the Southern Christian Leadership Conference, which had been led by the Rev. Dr. Martin Luther King Jr. before his death, to form his own organization, Operation PUSH, which first stood for People United to Save Humanity and later, People United to Serve Humanity (and which then merged with the Rainbow Coalition). Mr. Jackson, now 81, announced he would be shifting day-to-day leadership of the organization to the Rev. Dr. Frederick Haynes III, a Texas-based pastor, 62.

It has been 39 years since Mr. Jackson first ran for office, and yet what he stands for — a living link to the civil rights movement and a symbol of the work that remains to fulfill that movement’s dream of full equality for Black people in America — is something precious. Perhaps all the more so given that Mr. Jackson remains a complicated, little understood figure whose work is as misunderstood as it is seemingly ubiquitous.

Mr. Jackson left seminary to march beside Dr. King in Selma, Ala., eventually making his way into the inner circle. He was there on the day that Dr. King was killed, wearing a shirt he famously said was stained by Dr. King’s blood. From that moment on, he would use his extraordinary oratory skills and knack for attracting media attention to become one of the most well-known Black people in America and perhaps the world.

Mr. Jackson had been sent to Chicago by Dr. King in 1966 to manage Operation Breadbasket. It had a bold mission: to address the economic conditions of Black people. Tasked with moving the movement beyond the sit-ins and protests aimed at securing basic decency for Black people in the South, Breadbasket targeted substandard housing conditions, persistent de facto and de jure racial exclusion and the diversity of products that stocked the store shelves in minority communities.

Mr. Jackson learned from and expanded on tactics Dr. King pioneered. In 1966, Dr. King and his wife, Coretta, briefly lived in a dilapidated housing project in Chicago to highlight the treatment of poor Black people by landlords, prompting the city to crack down on substandard living conditions. Months later, the threat of peaceful marches through the all-white Chicago suburb Cicero aroused the fury of the American Nazi Party, which sought to form a counterprotest. The march was called off after Dr. King reached an agreement with Chicago leaders to open more housing in the city to Black people. President Lyndon Johnson rode the momentum of national mourning in the wake of Dr. King’s assassination to push Congress to approve the Fair Housing Act of 1968.

In the years after Dr. King’s murder, Operation Breadbasket’s boycotts and Mr. Jackson’s pickets of local businesses became legendary. Later the organization’s ambitions grew, and after Mr. Jackson’s break with S.C.L.C., he began to target more powerful interests, shifting to national companies such as Pepsico and the grocer A&P. A similar pattern played out in dozens of meetings with countless corporate entities over the course of decades. There were times when the simple threat of a meeting with Mr. Jackson would touch off a cascade of events that resulted in new opportunities for Black business owners seeking to buy into franchises and executives who were locked out of board positions and C-suite positions. At other times, seeking to avoid the heat, corporations proactively moved to diversify their boards or corporate ranks.

Mr. Jackson often said he considered himself a “tree shaker, not a jelly maker.” Those who worked for him knew the saying well: After all, they were the ones tasked with picking up the fruit from the floor to make the jelly.

Could anyone else shake the tree quite like Jesse Jackson? And even if they could, would America still value it? At a time when diversity is once again coming under political attack, the tactics that Mr. Jackson pioneered and the doors of opportunity he opened for countless women and people of color in corporate America are under attack as well.

Almost immediately after Dr. King’s death, Mr. Jackson moved to fill the vacuum that was left in the civil rights movement. But it wasn’t until more than a decade later that he began to look at politics. Mr. Jackson’s efforts to register voters in Chicago helped propel Harold Washington into office in 1983, making him the first Black mayor of that city. Mr. Jackson traversed the country to register voters, especially across the South. It would eventually fuel his unlikely national bid for the presidency. Despite years of living in Chicago, he never lost his South Carolina drawl or his connection to a network of Southern Black churches that sustained his ministry and activism. Mr. Jackson never actually pastored a congregation but ministered to a roving flock, preaching the virtues of civic engagement. His parable of unregistered voters (mostly in the South) as the pebbles in David’s slingshot in his fight against Goliath became a cornerstone of his presidential campaigns.

Mr. Jackson’s political influence was felt most acutely on the left, which has been shaped by the ideas he ran on in his presidential campaigns, his emphasis on increasing the electorate through widespread voter registration of youth and people of color, and by the scores of people who at some point made their way through his orbit. Among them: cabinet members like former Labor Secretary Alexis Herman, Representative Maxine Waters, the political strategist Donna Brazile and Housing and Urban Development Secretary Marcia Fudge.

Many Americans, especially Black people, remember the spectacle of Mr. Jackson’s presidential ambitions: the massive rallies, the chants of “Run, Jesse, run!” But those campaigns also merged a unique platform of economic populism, social justice and moral urgency. While Mr. Jackson did successfully mobilize and energize Black voters, his candidacy is best remembered for mobilizing voters not on the basis of race but on moral imperatives and policy prescriptions that when compared with those of today’s Democratic Party seem prescient.

The shorthand of Mr. Jackson’s historic candidacies in the 1980s labels him correctly as the most serious Black candidate for the presidency until Barack Obama emerged two decades later. But Mr. Jackson’s greatest achievement was not, as some thought, his race but the policy platform he built. In 1984 and 1988, he ran to end economic inequality, introduce universal health care and promote America first policies that would have echoes in the decades to come. He envisioned a coalition of Black, white, Asian, Native, rural, urban, gay and straight people coming together to achieve social justice as much as economic justice.

“When we form a great quilt of unity and common ground, we’ll have the power to bring about health care and housing and jobs and education and hope to our nation,” Mr. Jackson said in his speech at the 1988 Democratic Convention. His unsuccessful campaigns had a concrete consequence: Mr. Jackson negotiated permanent changes to the Democratic Party’s nominating process, including ending its winner-take-all primary system, which made Barack Obama’s first victory in the Democratic primary possible. By the time of Mr. Obama’s run for office, an entire generation of Black Americans had seen and hoped for a Black man in the White House. “We lifted the low ceiling higher,” Mr. Jackson mused to me recently. “We lifted the ceiling up on Black possibility.”

Abby D. Phillip is senior political correspondent and anchor of “Inside Politics” on CNN. She is writing a book on Jesse Jackson’s legacy in American politics.

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