COLUMBIA, S.C. — Several Democratic presidential candidates briefly put aside their recent sparring on Monday and marched arm in arm through the streets of South Carolina’s capital to honor the Rev. Dr. Martin Luther King Jr., whom they later invoked in speeches about America’s past and future that were rich with election-year overtones.
As the six-block march began from the Zion Baptist Church to the State House, where a Confederate flag once flew over the dome, Senator Bernie Sanders looped an arm through Senator Elizabeth Warren’s elbow, as the two joined other candidates in singing “We Shall Overcome” for part of the trip. Representative Tulsi Gabbard and Senator Amy Klobuchar each locked elbows with former Vice President Joseph R. Biden Jr. as well.
The sight of Mr. Sanders and Ms. Warren shoulder to shoulder — after a week in which they argued over their recollections of a private conversation about whether a woman could win the presidency — delighted Lisa Ray Clarkson, a retired teacher from Norfolk, Va., who was at the march.
“That means they have gotten over their differences and the Democratic Party is reuniting,” Ms. Clarkson said as she walked alongside the procession to the State House, where several thousand people converged.
It was a hopeful sentiment for a Democratic field that has become noticeably more fractious in the final weeks before the Feb. 3 caucuses in Iowa, where Mr. Biden, Ms. Warren, Mr. Sanders and former Mayor Pete Buttigieg of South Bend, Ind., are bunched tightly in polls and campaigned on Monday afternoon.
In addition to the Warren-Sanders argument, Mr. Biden and Mr. Sanders have been criticizing each other’s records, with Mr. Sanders trying to cut into Mr. Biden’s support among older voters and black voters by portraying the former vice president as open to cuts in Social Security. Mr. Biden has denied that and demanded an apology from Mr. Sanders, who has stood firm.
On Monday in Iowa, Mr. Biden, who over the course of his career has at times supported Social Security freezes, vowed, “There will be no compromise on cutting Medicare or Social Security.”
Tensions also flared on Monday after the Sanders campaign circulated an op-ed written by Zephyr Teachout, an associate professor at Fordham Law School and a former New York political candidate, that accused Mr. Biden of having a “big corruption problem.” Ron Klain, a top Biden adviser, responded on Twitter: “There are a lot of legitimate issues to debate in 2020. But the only two campaigns ever to call @Joebiden “corrupt” are Trump and Sanders. What does that tell you?”
Mr. Sanders took the step of apologizing to Mr. Biden in an interview with CBS News. “It is absolutely not my view that Joe is corrupt in any way. And I’m sorry that that op-ed appeared,” Mr. Sanders said in the interview, which went online Monday night. Ms. Teachout is a longtime Sanders supporter whom the Vermont senator backed in a congressional race in 2016.
Mr. Biden suggested he had accepted Mr. Sanders’s apology, writing on Twitter: “Thanks for acknowledging this, Bernie. These kinds of attacks have no place in this primary. Let’s all keep our focus on making Donald Trump a one-term president.”
The four leading candidates in the polls are competing hard in South Carolina, particularly for support from black voters, who will make up a majority of the Democratic primary vote in the state on Feb. 29. Mr. Biden has a strong lead in South Carolina polls and is widely favored among black voters. None of his rivals took him on frontally on Monday, but instead sought to make the case to African-Americans and others in South Carolina about how the next president could benefit their interests.
Mr. Sanders, addressing the enthusiastic crowd on a cold day at the State House, reminded onlookers of Dr. King’s legacy of courage and opposition to the Vietnam War, which the 78-year-old Vermont senator also denounced. While Mr. Sanders has been trying to draw a contrast with Mr. Biden on their records on military action, he focused more on Monday on President Trump.
“If we do not allow Trump and his friends to divide us up by the color of our skin, or where we were born, or our sexual orientation or religion, if we stand together there is nothing we cannot accomplish in the fight for racial justice, social justice,” Mr. Sanders said.
Ms. Klobuchar, of Minnesota, invoked Dr. King’s comment that Americans are “all tied in a single garment of destiny — what affects one directly affects all indirectly,” and said that rising hatred across the nation would ultimately wound everyone.
“It coarsens our civic life. You can see it in the senseless racist shooting of worshipers in Charleston, you can see it in that rabbi’s home and stabbing, you see it in that bombing of the mosque in Minnesota, you see it at the riot in Charlottesville,” she said.
Addressing Mr. Trump directly over his comment in 2017 that “both sides” were to blame for the violence in Charlottesville that killed Heather Heyer, who was protesting a white supremacist rally there, Ms. Klobuchar said: “And no, there are not many sides to blame, Mr. President, when one side is the Ku Klux Klan. There is only one side, and that is the American side. That is it. That is all.”
Before the march and State House speeches, several candidates told a breakfast gathering of predominantly black voters that they were committed to advancing Dr. King’s legacy and that defeating Mr. Trump in November was a crucial step toward that goal.
“My campaign revolves around the image of the first day that the sun comes up over South Carolina and our country and Donald Trump is no longer the president of the United States,” Mr. Buttigieg said at the Columbia Urban League’s annual King breakfast. “I raise the image of that sunrise because it will bring forth the burning question Dr. King posed in the summer of 1967: Where do we go from here?”
“Because on that day our country will be even more polarized and torn up than it is now,” said Mr. Buttigieg, who is one of the top-polling candidates in Iowa but is struggling in South Carolina and among black voters. He urged action to combat disparate treatment by race in the health care system and to address environmental pollution disproportionately affecting African-Americans, who make up a majority of the Democratic primary electorate in the state.
Former Gov. Deval Patrick of Massachusetts, the only black candidate still in the Democratic field, took a different tack, telling the breakfast audience, “If we are really going to deliver a future for our children and grandchildren consistent with the values of equality, opportunity and fair play, to which Dr. King and the Urban League served as examples, then we’re going to have to start rejecting false choices.”
“Prosperity and justice can live alongside each other,” he said. “The notion that you have to hate business to be a social justice warrior or hate police to believe black lives matter are ridiculous.”
After the South Carolina events, most of the candidates flew quickly to Iowa to attend the 2020 Iowa Brown & Black Democratic Presidential Forum on Monday afternoon.
Mr. Biden, who repeatedly noted his commanding lead in polls with African-American voters over all, objected when moderators at the event noted Mr. Sanders’s strength with younger black voters. He also spoke about his heartfelt connection to black Americans, while acknowledging that he could not “fully understand” their experience.
“I know enough to know and see the pain, you can see the pain in people’s eyes,” he said. “I’m not saying, ‘I am black.’ But I want to tell you something. I have spent my whole career with the black community.”
“They know me,” he said firmly. “They know where my heart is. And they know what I’ve done.”
Mr. Buttigieg was pressed about his mayoral record in South Bend, specifically regarding his decision to fire a black police chief and his handling of racial divisions within the department. At times, the questioning even seemed contentious, as Mr. Buttigieg refused to go into detail about specific personnel decisions.
Mr. Buttigieg acknowledged fault on one point: the decrease in the number of black police officers during his tenure.
“This is an area where I’ve admitted it’s not where I wanted to be,” he said.
Mr. Sanders faced a question about the president’s wall on the southern border, and whether it would be a powerful statement if the existing barrier were taken down. “I don’t know, maybe the answer is yes,” he said, adding that if it cost “billions of dollars to tear it down, maybe the money would be better spent on child care in this country.”
Mr. Sanders also spoke about his immigration plans, which include a moratorium on deportations, and said there could be exceptions to the moratorium if an undocumented immigrant were convicted of a “terrible, terrible” crime.
But he noted that his immigration stance could leave him open to attack in a general election. “This is an issue, of course, something Trump will jump all over,” he said.
The forum ended on a lighter note when Ms. Klobuchar was asked about the last time she had smoked marijuana.
“Uh, you’d have to go back to college days,” she said to laughter.
Reporting was contributed by Jonathan Martin from Columbia, S.C., Lisa Lerer from Washington, and Katie Glueck, Jennifer Medina and Astead W. Herndon from Des Moines.