Democratic presidential aspirants fanned out across the country on Monday to praise the legacy of the Rev. Martin Luther King Jr. and offer direct appeals to black voters who will play a major role in deciding on a nominee to challenge President Trump.

They brought different styles and points of emphasis but collectively laid out markers that will shape the primary debates and the 2020 general election, attacking Trump for fomenting racism, condemning systemic discrimination and highlighting King’s crusade for economic justice, among other things.

Former vice president Joe Biden and former New York mayor Michael Bloomberg called for more racial justice and poverty reduction at an event in Washington. Declared candidate Sen. Elizabeth Warren (D-Mass.) called for a constitutional amendment to guarantee the right to vote at an event in Boston, while another contender, Sen. Kirsten Gillibrand (D-N.Y.), called on “white women like me” to bear the burden of fighting racial injustice at a New York event.

See how the Rev. Martin Luther King Jr. is being honored on his national day of remembrance

Jan. 21, 2019 | From left, Ballou High School student Ayisha Lee, Ron Brown student Dominic Paris and Isha Lee, special initiatives director for Serve DC, in the D.C. mayor’s office on volunteerism, paint columns in a hallway during the Martin Luther King Jr. National Day of Service at Ron Brown College Preparatory High School. (Katherine Frey/The Washington Post)

Two other potential candidates, Sens. Bernie Sanders (I-Vt.) and Cory Booker (D-N.J.) sat side by side in the front, middle pew at Zion Baptist Church in Columbia, S.C., for the King holiday prayer service and then spoke at a later event.

“Today we talk about justice, and today we talk about racism,” Sanders said. “I must tell you it gives me no pleasure to tell you that we now have a president of the United States who is a racist.”

The outreach came on a day suffused with political commemorations. Sen. Kamala D. Harris (D-Calif.) became the first black candidate this year to declare a campaign for the presidency, choosing the holiday to underscore the history-making potential of her bid.

Trump and Vice President Pence briefly visited the King memorial in Washington for a wreath-laying near the statue of the slain civil rights leader. They made no formal remarks.

Former vice president Joe Biden and former New York mayor Michael Bloomberg called for racial justice at the National Action Network's MLK Breakfast on Jan. 21. (AP)

“Good morning, everybody. Great day. Beautiful day. Thank you for being here. Appreciate it,” the president said before departing.

Black voters will have a key role in the Democratic primary campaign. They made up about 1 in 4 primary voters and caucusgoers, on average, in the 2016 nomination fight. In some Southern states, including early-voting South Carolina, blacks represent a majority of the Democratic electorate.

“You cannot in 2019 and 2020 get away with not talking about race,” said Symone Sanders, a black Democratic strategist who worked for Sanders in 2016 and has not yet picked a candidate this cycle. “What you are saying in Iowa should not look painstakingly different from what you are saying in South Carolina.”

To accomplish this goal, the candidates and potential entrants have started to hone their messages. In her hometown of Boston, Warren argued that King’s struggle continues today.

“We are the heirs of Dr. King’s dream and soldiers in the fight for justice and equality,” Warren said. “As we speak, our government is shut down for one reason: so that the president of the United States can fund a monument to hate and division along our southern border.”

Later in the afternoon, Gillibrand appeared with the Rev. Al Sharpton at an event in New York, where she said she felt called to fight a president who has “inspired a hate and a darkness in this country that I have never experienced myself.”

“We will put on the breastplate of righteousness because we know right from wrong,” Gillibrand said. “We will wield the sword of the spirit.”

In South Carolina, Booker also described the moment as calling for moral leadership.

“We are dissatisfied that we live in a nation where you get a better justice system if you’re rich and guilty than poor and innocent. We are dissatisfied that all over America, thousands of children find it easier to find unleaded gasoline than unleaded water. We are dissatisfied that we are giving tax breaks to millionaires and billionaires,” Booker said. “Our dissatisfaction needs to turn into action.”

Several attendees at Zion’s morning service said they were particularly excited about the black politicians looking to run as Democrats in 2020.

The Rev. Amiri B. Hooker of Camden, S.C., said he was encouraged by the Harris candidacy.

“I think she’s going to shake up a whole lot of folks,” Hooker said. “I like Bernie, but I think Bernie represents an old school of politics. I think she and Booker are strong African American leaders.”

At a news conference on Monday at Howard University, the historically black college she attended, Harris said she would not have to choose between a campaign that connects with black voters and one that makes broader appeals.

She has a mother from India and a Jamaican father, and when asked how she identified, she said “proud American.”

“We must understand that based on where they are — geographic regions, be it gender or race or ethnicity — there may be a diversity of issues and concerns,” she said. “We should be true to those concerns. Fundamentally, we should also understand that the vast majority of us have much more in common than what separates us.”

Before the mostly black audience at the morning’s National Action Network event in Washington, Biden and Bloomberg both admitted mistakes in their past records and laid out different policy focuses that would play a central role in their campaigns.

“We have a lot to root out, most of all systematic racism that most of us whites don’t even like to acknowledge even exists,” Biden said. “It’s been built into every aspect of our system.”

Bloomberg echoed the call, talking about his recent visit to Tulsa to commemorate the 1921 race riot that historians say killed more than 100 African Americans. “We need to face up to history,” Bloomberg said. “The pace of progress is still too slow, but there is not a doubt in my mind that it is possible to accelerate the pace.”

Biden repeated his regret over supporting tough-on-crime measures in the 1990s, which he has admitted worsened racial sentencing disparities. Biden successfully fought in 2010 to roll back the different guidelines in federal criminal sentencing for powder cocaine and crack cocaine that he had previously supported.

“I haven’t always been right,” Biden said. “I know we haven’t always gotten things right.”

He spoke about focusing on bail reform, boosting the minimum wage and increasing federal funding for vocational training as ways to reduce racial inequities.

Bloomberg said he could not argue that “every decision I have made as mayor was perfect,” though he did not specifically distance himself from the stop-and-frisk policing policy he supported over the objections of civil rights leaders such as Sharpton.

Instead, he talked about his efforts to improve schools in New York, reduce pollution in black and Hispanic neighborhoods and his leading role in funding groups that advocate for gun regulation.

“Dr. King is still our drum major for justice,” Bloomberg said. “To truly celebrate the way he lived, we must redeem how he died.”

In a sprawling field, Bloomberg and Biden would find themselves competing for a similar slice of the Democratic electorate should they decide to run. But Bloomberg said he expected to keep their disagreements civil.

“Whatever the next year brings for Joe and me, I know that we will both keep our eyes on the real prize, and that is electing a Democrat to the White House in 2020,” Bloomberg said.

Sharpton, who has fashioned himself as a principal emissary for potential Democratic nominees hoping to reach black voters, said he was excited for the coming primary campaign, which he predicted could yield surprising results.

“Because the Trump administration has appeared so hostile, a lot of blacks are looking at who can win rather than just having a view on a set of issues that they might think are selectively important,” Sharpton said in an interview with The Washington Post. “It’s going to be a very interesting few months.”

Linskey reported from Columbia, S.C. Chelsea Janes contributed to this report.