Emanuel African Methodist Episcopal Church in Charleston, S.C., the oldest A.M.E. church in the South, will forever be associated with former President Barack Obama because of his memorable — and melodic — eulogy for the nine victims of a racist massacre in its fellowship hall in June 2015.But it is Joseph R. Biden Jr. who will become the first sitting president to speak at the storied church, when he delivers a campaign address there Monday about threats to American democracy, including those posed by political and hate-fueled violence.Mr. Obama made his contemplative remarks about race, and warbled his way through “Amazing Grace,” not at the site on Calhoun Street that the congregation bought in 1865, but around the corner at a college arena. Now, Mr. Biden will speak as president in the creaky old sanctuary itself, backed by towering stained glass one floor above the scene of the blood bath, a setting that conveys a mosaic of messages as he seeks to re-energize his African American base.Mr. Biden is far from the first to make a political case from Emanuel’s pulpit. His predecessors include Booker T. Washington in 1909, W.E.B. Du Bois in 1922 and the Rev. Dr. Martin Luther King Jr. in 1962.The church’s founding pastor, the Rev. Richard Harvey Cain, used it as a springboard to Congress during Reconstruction. Its civil rights-era pastor, the Rev. Benjamin J. Glover, simultaneously led the local N.A.A.C.P. and staged anti-discrimination marches from its steps. The Rev. Clementa C. Pinckney, the pastor who welcomed 21-year-old Dylann Roof into Bible study and was first shot by him, also was a long-tenured state senator, the youngest African American elected to South Carolina’s Legislature.The Biden campaign’s choice of Emanuel intends to show common cause with Black voters, who polls suggest have lost a measure of enthusiasm for the president. South Carolina, where African Americans make up about 60 percent of the Democratic electorate, hosts the party’s first-in-the-nation primary on Feb. 3.Before the shootings in 2015, Emanuel stood as an exemplar of two centuries of Black resistance to enslavement, oppression and discrimination. Its long history highlighted the essential role played by the Black church in freedom movements across the 19th and 20th centuries.A Sunday service at Mother Emanuel in October 2016. Stephen B. Morton for The New York TimesThe congregation began to form in 1817 in the commercial heart of the slave trade after a bold breakaway by free and enslaved Black people from white-controlled churches. Its first home on Charleston’s East Side was ordered destroyed by city officials in 1822 after they concluded that a foiled slave insurrection had incubated within the “African Church.” The accused ringleader, a free Black carpenter named Denmark Vesey, was hanged along with 34 others, many of them church members.The congregation reconstituted as Emanuel immediately after the Civil War, when A.M.E. missionaries followed Union troops into a bombed-out Charleston. It soon seeded other churches across the Lowcountry, earning the nickname “Mother Emanuel.”After the murderous rampage by Mr. Roof — who sits on death row in a federal penitentiary — Emanuel evolved into a different kind of symbol, of the persistence of racial violence in a post-civil rights age. And when family members of five of the victims showed up at Mr. Roof’s bond hearing and expressed forgiveness for the unrepentant white supremacist, the church came to embody their breathtaking expression of Christian grace.Those families and survivors of the shootings have been invited to visit with Mr. Biden in the sanctuary after the speech. He also is expected to meet with ministers in the fellowship hall, which is little changed from the night of the attack.By setting his speech at Mother Emanuel, Mr. Biden “emphasizes that there is still work to be done, a reminder that even though we’re in the 21st century we still have some 19th century minds in America,” said the Rev. Joseph A. Darby, a prominent A.M.E. minister in Charleston and longtime Biden supporter.Like many Americans, Mr. Biden was deeply affected by the events of June 2015. Seventeen days before the shootings, he had lost his elder son, Beau, to brain cancer. As vice president, he and his wife, Dr. Jill Biden, attended the memorial service that featured the Obama eulogy. They had happened to be vacationing nearby on Kiawah Island, and Mr. Biden returned to Charleston two days later to worship with Emanuel’s congregants. He made clear that his own mourning had melded with theirs. He had come to show the administration’s solidarity, he said, but also “to draw some strength from all of you.”Mr. Biden recounted that experience at a key juncture in the 2020 campaign, shortly before the crucial South Carolina primary, in a poignant televised exchange with the Rev. Anthony Thompson, the widower of one of the Emanuel victims. He characterized the forgiveness expressed by Mr. Thompson and others as “the ultimate act of Christian charity.”A church school class at Mother Emanuel in late 2015. A framed picture with portraits of the nine people who were killed there is hanging on the wall.Stephen B. Morton for The New York TimesMr. Biden’s victory in South Carolina, owing largely to Black voters, righted his listing campaign after losses in earlier contests. Although he did not visit Emanuel during that race, eight of his Democratic challengers did.Emanuel has become totemic in debates over combating hate crimes and gun violence, with the Rev. Eric S.C. Manning and survivors of the attacks keeping high profiles. One of those five survivors, 79-year-old Polly Sheppard, said of Mr. Biden’s visit that “it’s an honor that the victims and survivors are remembered by the president and people across the nation.”More than eight years after Emanuel was thrust into an unwanted spotlight, the congregation remains in recovery. Church leaders now juggle weddings and funerals with the burdens of administering what has become an international shrine. Tour buses arrive during the week; visitors, many of them white, nearly outnumber members in the pews some Sundays.The congregation, already shrinking thanks to an aging membership and the gentrification of downtown Charleston, numbers only 576, down from more than 2,000 in the 1950s. The Covid pandemic converted many into Sunday-morning streamers. A fourth of the roughly 100 worshipers at this week’s service were visitors.Pastor Manning has led a multiyear effort to raise millions to repair severe termite damage in the trusses and start other renovations. The first phase, finished last year, made it safe to reoccupy the choir loft, but left the church $870,000 in debt. Separately, a foundation has been raising $25 million to build a memorial to the Emanuel shooting victims, designed by the architect Michael Arad, best known for the National September 11 Memorial and Museum in New York. Ground was broken recently in the church parking lot.The memorial’s purpose, and Mother Emanuel’s story, dovetail with Mr. Biden’s political message, said Representative James E. Clyburn of South Carolina, an A.M.E. member whose district includes the church.“The act of violent extremism that took the lives of nine innocent worshipers at Mother Emanuel A.M.E. Church could have torn this community and the country apart,” Mr. Clyburn said. “Instead, the victims and impacted families brought the Charleston community together in a moment of darkness and responded with hope and resilience. There are lessons to be learned from the tragedy that took place on this holy ground.” More