ATLANTA, Georgia (CNN) -- At the annual Martin Luther King Jr. memorial service Monday in Atlanta, former President Bill Clinton spoke in broad terms about the presidential race, while a more pointed political message came from a prominent supporter of Sen. Barack Obama.
Clinton, introduced by King's nephew, Isaac Farris, as a man whose "presidency truly reflected the principles of Martin Luther King Jr.," cited the diverse field of Democratic candidates seeking the presidential nomination.
"It's all possible because of Martin Luther King's vision of the beloved community," Farris told the crowd at Ebenezer Baptist Church in Atlanta.
"This is a time for humility, because there are many storm clouds on the horizon at home and around the world," Farris said. "And we still talk better than we do. We still talk better than we do. All of us. Every last one of us." Watch Democrats talk about MLK legacy »
Clinton's speech, largely a reflection on how King had touched his life as a young man and guided his career, followed Atlanta Mayor Shirley Franklin's address. She has endorsed Obama, but her comments praised the progress made possible by King.
"We are about to witness the impossible being probable," she told the crowd in the church where King once preached.
Franklin said in times of trouble, America "stretches to elect a president from uncharted places -- a mill worker's son, a first lady, a Mormon, a Baptist preacher, and even, ladies and gentlemen, a black man."
She added, "We are at the cusp of turning the impossible into reality. ... Yes this is reality, not fantasy or fairy tales."
On the campaign trail with his wife, Sen. Hillary Clinton of New York, earlier this month, Bill Clinton had called the Illinois senator's representation of his position on the Iraq war a "fairy tale." Some African-Americans said they viewed the remark as an assessment of Obama's candidacy in general. Clinton denied that was what he meant.
Both candidates last week called on their supporters to end bickering between the campaigns.
South Carolina Rep. James Clyburn, the highest-ranking African-American in Congress, told CNN's Wolf Blitzer Monday that Bill Clinton should "tone it down," when criticizing Obama.
"He is causing a lot of anxiety among the base that exists in our party," he said.
After Franklin spoke Monday, many in the congregation stood and applauded, though Clinton remained seated, applauding politely.
At the Ebenezer service, campaigning for candidates is not invited, but general political messages flow freely. During Clinton's introduction, Farris -- president and chief executive of the King Center -- noted Clinton would speak "in his role as former president," rather than as the spouse of a candidate.
When Clinton took the floor to a standing ovation, he noted many dignitaries present by name, and joked that Franklin "already took care of whatever political dilemma I have" in participating at the service during a campaign year.
"I wouldn't have said it quite the way she did, but she got it all out there, that was good," he said smiling.
Republican presidential hopeful former Arkansas Gov. Mike Huckabee also attended. "I think America owes a lot to Dr. King," he told reporters outside the church.
"When politicians were brought basically dragging and kicking to the whole civil rights movement, it was Dr. King that really led this country to recognize the worth and value of every human being."
Asked why more Republicans don't reach out to black voters, he responded, "I can't speak for them, I can only speak for myself. ... Politics shouldn't be anything other than making sure that every single human being, every American, has the same opportunities."
Clinton noted the presence of his fellow former Arkansas governor.
"We don't agree on much, but he is a very good man," Clinton said of Huckabee, noting they had both worked on programs to combat obesity.
The three leading Democratic presidential candidates, meanwhile, took part in a King rally in South Carolina, the state that serves as the next showdown in their fight for the nomination.
On Sunday, Obama spoke at a service at Ebenezer Baptist, while former Sen. John Edwards of North Carolina visited a service at Zion Baptist Church in Columbia, South Carolina, and Hillary Clinton picked up the endorsement of Pastor Calvin Butts of Abyssinian Baptist Church, a prominent African-American congregation in New York. E-mail to a friend