BOSTON — Representative John Lewis helped change America as a passionate civil rights activist before his tenure in Congress, but Saturday afternoon, inside the brick-lined walls of Twelfth Baptist Church, the Georgia lawmaker made a rare case for traditionalism and seniority.
“People who have been around for awhile, they know their way around,” Mr. Lewis said. “They know where all the bodies are buried and they know how to get things done.”
Mr. Lewis had come to Twelfth Baptist to campaign for Representative Michael E. Capuano, the liberal Democrat who faces a grueling primary challenge from Ayanna Pressley, a progressive Boston City Council member who is trying to become the state’s first nonwhite member of the House of Representatives.
On Saturday, Mr. Lewis lent his voice to the argument that Mr. Capuano’s experience and seniority were needed in the Democrats’ fight against President Trump, rather than the youthful energy of Ms. Pressley’s grass-roots campaign.
“It’s important to keep a leader, a fighter, and warrior like Mike Capuano around,” Mr. Lewis said at the event, which was equal parts gospel service and political town hall and held at the same Massachusetts church where the Rev. Martin Luther King Jr. once served as an assistant pastor in the 1950s.
His argument is emblematic of the bitter intraparty debates that Democrats are having across the country ahead of the 2018 midterm elections — debates that often split liberals across the touchy fault lines of race, age and gender. The campaign appearance by Mr. Lewis and the recent decision by the political arm of the Congressional Black Caucus to back Mr. Capuano has made this primary race a microcosm of a larger search for identity among Democrats, while igniting friction between national black politicians and local ones.
The Seventh Congressional District that is up for grabs stretches from Boston’s Dorchester and Roxbury neighborhoods to the communities of Cambridge and Somerville across the Charles River. It is the state’s only district where the majority of residents are not white and Mr. Capuano, who is white, has never faced a serious primary challenger in his 10-term tenure in Congress.
Then came the bid by Ms. Pressley, who was the first woman of color to be elected to the City Council in its 108-year history. But instead of rallying around her, high-profile black politicians — including Mr. Lewis, Representative Maxine Waters of California and former Gov. Deval Patrick of Massachusetts — have all endorsed her white opponent.
Mr. Lewis declined several requests to discuss his endorsement. Representative Gregory W. Meeks of New York, the chairman of the black caucus’s political action committee, said the group endorsed Mr. Capuano largely because of his longtime personal relationships with its members and his senior position on the House Financial Services Committee.
“We have nothing against the challenger, but when you have a colleague that’s done the right thing for 20 years, and has worked with you intimately, there’s not a reason for us to not endorse him,” Mr. Meeks said. “We know him.”
Mr. Meeks said that while he supported increasing diversity in the House, new candidates should focus on unseating Republicans — not on defeating “a Democrat who has worked hard in the caucus” like Mr. Capuano.
“It’s not just about new blood,” Mr. Meeks said. “We need young and energetic folks to run in open seats, or seats that Republicans currently hold.” The Seventh District is reliably Democratic and figures to go to whichever Democrat prevails in the primary.
Still, the endorsements have prompted a backlash locally from those who believe that the Democratic Party is failing to live up to its oft-repeated rhetoric regarding the importance of diversity.
Among Boston’s tight-knit black political community, Marie St. Fleur, a former state representative and the first Haitian-American elected to statewide office in the country, posted a statement on social media questioning the black caucus’s understanding of local issues. Bennie Wiley, a powerful civic leader in Massachusetts who is supporting Ms. Pressley’s campaign, said she was “disappointed, but not surprised” in the actions of the black caucus.
Ms. Wiley said she would rather the caucus follow the lead of the state’s two senators, Elizabeth Warren and Edward J. Markey, and decline to endorse either candidate.
“I understand people feel they have to be loyal,” Ms. Wiley said. “But I was disappointed.”
Ministers at the Twelfth Baptist Church said that while they respect and admire Mr. Lewis and the black caucus, the decision to so publicly back Mr. Capuano, and snub Ms. Pressley, had caused concern. One associate pastor, the Rev. Jeffrey L. Brown, decided not to attend Saturday’s town hall, and said the optics of blocking a viable campaign by a black woman in 2018 were at best divisive and at worst hypocritical.
“For me, I kind of recoil and I know many leaders recoil at the idea that we’re supposed to sit back and wait our turn because someone else has voted within our interests,” Mr. Brown said.
The Rev. Willie Bodrick II, another associate pastor at the church, said he thought the endorsements of Mr. Capuano were “hasty.” Though he attended the town hall with Mr. Lewis, he characterized the primary race between Mr. Capuano and Ms. Pressley as one that exposes the generational gap in the Democratic Party, as a respected elder statesman in the House backs a 66-year-old incumbent over a challenger more than 20 years younger.
“The generational struggle, this pull and tug, is showing itself across the board here,” Mr. Bodrick said. “This is about just what kind of party the Democratic Party wants to be.”
One person who says she is not rattled by the high-stakes political gamesmanship, however, is Ms. Pressley herself. In an interview one day after the black caucus endorsed her opponent, Ms. Pressley said she understood that her road to unseating a longtime incumbent would be a lonely one, considering the vast amount of personal relationships Mr. Capuano has amassed over his nearly two decades in Congress.
She pointed to Mr. Lewis’s own life as a civil rights activist as inspiration for her to disrupt “the establishment,” and shrugged off the idea that out-of-state endorsements — even from prominent black lawmakers — would significantly affect the race.
“I just gave a commencement speech, and the young people I was with in that room, the young professionals I was with yesterday, and the artists and entrepreneurs I was with the day before that — that’s my C.B.C.,” Ms. Pressley said.
“This is between me and the voters.”