In exactly two weeks, the first votes of the 2020 Democratic primary will be cast in Iowa. And while they may be fierce rivals, the candidates pushed a message of harmony at Martin Luther King Jr. Day events on Monday.

Senators Bernie Sanders and Elizabeth Warren, who sparred last week over alleged comments made at a 2018 meeting, walked arm in arm at a parade in Columbia, South Carolina. Former New York Mayor Michael Bloomberg marched in Little Rock, Arkansas.

In Iowa, the rest of the field addressed leaders of the state's small black and Latino communities.

"Let's not pretend that if we, when we replace this president that everything is just going to get better. Because a lot of these problems have been mounting for a long time," said Pete Buttigieg.

President Trump also paid respects to Martin Luther King Jr., with a visit to the reverend's memorial in Washington, D.C., on Monday afternoon.

Democratic presidential candidates, former Vice President Joe Biden, left, Senators Amy Klobuchar, Elizabeth Warren and Bernie Sanders march down Main St. to the King Day at the Dome event on January 20, 2020, in Columbia, South Carolina. Sean Rayford / Getty

Nationwide, former Vice President Joe Biden holds a commanding lead among black voters — the most loyal Democratic voting bloc. "To paraphrase Dr. King, we have guided missiles, but we have misguided men leading this nation," Biden said Monday.

He also has a lead among seniors, despite recent accusations from Sanders that he wants to make cuts to social security.

"Time and time again, Joe Biden has been clear in supporting cuts to social security," Sanders said.

"I have been a gigantic supporter of social security from the beginning," Biden said in response.