For a few hours yesterday during a Martin Luther King Jr. Day celebration in Harlem, Council Member Charles Barron could have been mistaken for the mayoral front-runner.

Not only did he get a glowing introduction – and an informal endorsement – from the Reverend Al Sharpton, who was host of the event at the Canaan Baptist Church, but Mr. Barron also had the crowd in vocal agreement as he called for change in the “power structure” of the city.

In the polls, Mr. Barron, who is black, finishes dead last among the five Democrats vying for the party nomination. Still, the appearances at Martin Luther King Day events of the other four Democratic mayoral contenders, and of the incumbent, underscored that they all have catching up to do among the Brooklyn politician’s African-American base.

Mayor Bloomberg, a Republican, and his field of challengers spent the day crisscrossing the city to deliver speeches that invoked Martin Luther King Jr.’s civil-rights record in promoting programs they support, policies they oppose, and wrongs they hope to right. Many of their speeches were framed in a what-would-King-have-done vein.

Mr. Bloomberg was paying his fourth King Day visit to Canaan, and Rev. Sharpton seemed to take special delight in needling him.

“We may not always agree with you on everything, but we’re all agreeable on King Day and we all are able to stand together,” the preacher said.

At events throughout the day, Mr. Bloomberg said the city was going in the “right direction” with a “booming” economy and opportunity for all.

The Democrats portrayed a very different city and used their platform to attack the mayor on everything from his education policies to his proposal to build a football stadium on the West Side of Manhattan, all of which they characterized as especially bad for minority groups.

The speaker of the City Council, Gifford Miller, for example, said the mayor’s unemployment numbers did not tell the whole picture.

“The government will tell you that the unemployment rate is at a low, 6%, 5%,” he told a crowd in Brooklyn earlier in the day.

“But,” he said, citing a figure that cropped up in different speeches throughout the day, “49% of African-American men in this city do not have a job. And what I find more troubling than that statistic is the silence of our leaders in response.”

A former president of the Bronx, Fernando Ferrer, said the government’s role is to “extend its hand of protection and comfort to those who need us most.”

“A billionaire does not,” Mr. Ferrer said, in a clear reference to the mayor. “People who are sleeping on the no. 6 subway do.”

Mr. Ferrer, who lost in the 2001 Democratic primary run-off to Mark Green, said the “uncomfortable” questions asked by King cannot be ignored now.

“That fight continues today. If he were here he might be saying, ‘Have we all gone mad, New York?’ We’re getting ready to spend hundreds of millions of dollars on a football team on the West Side … and people are going without a meal.”

The event, which drew dozens of elected officials, was a Sharpton-driven show. Candidates seeking re-election, candidates running for new offices, and candidates who had already won, all took the chance to share the stage with a controversial leader and to woo the crowd. Even Mr. Green, whose campaign four years ago was accused of giving out racially divisive fliers to make Mr. Ferrer look beholden to Mr. Sharpton, attended. Mr. Sharpton introduced Mr. Green, who has expressed interest in running for New York attorney general next year, but did not invite him to speak.

Each of the mayoral candidates delivered remarks and then fielded questions. Rep. Anthony Weiner, who represents a Brooklyn-Queens district, said King would be both “grateful” for the progress made in advancing civil rights and “unsatisfied” that poverty still affects minority communities.

As Senator Clinton did earlier in the day at the Brooklyn Academy of Music, Mr. Weiner said the presidential election results in Ohio need to be re-examined. He said he did not dispute President Bush’s victory, but stressed that it was crucial to the democratic process to ensure that there were no problems with voting. He also said the $50 million to be spent on the president’s inaugural festivities this week constituted an “act of vanity.”

The other African-American candidate for mayor, Borough President C. Virginia Fields of Manhattan, was the last mayoral candidate to speak. As Mr. Barron did, she said members of minority groups were being left out of the senior ranks of government.

One member of the audience, Debra Smith, 39, of Brooklyn, said she planned to vote for Mr. Barron, but she complained that there were plenty of issues the candidates did not address. And she wondered whether they were coming simply to court votes.