Kicking off his reelection bid with a speech to supporters Saturday, Mayor Vincent C. Gray didn’t receive a standing ovation when he mentioned a rise in public school test scores or a decline in unemployment. But when he apologized for the “pain and suffering” caused by his 2010 campaign, hundreds of backers leapt to their feet and chanted, “Four more years!”

“I think it’s time now, ladies and gentlemen, to turn the page,” Gray said at the rally, the first public event of his late-developing reelection campaign.

The apology, delivered at a Southeast Washington community center, was an acknowledgment that the Democratic primary may well be decided by the electorate’s willingness to look past the campaign scandals and ongoing federal investigation that have defined much of his term. For his backers, the applause reflected the hope that the apology will prompt voters to move on, even if investigators don’t.

Gray offered relatively brief remarks, about 20 minutes’ worth, after introductions from his campaign chairman, lawyer Jerry A. Moore III, and longtime friend and activist Carrie Thornhill. He highlighted progress in the city during his three years as mayor, including higher public-school test scores, lower unemployment and a growing population.

First, however, Gray addressed his 2010 campaign, the source of political head winds that made his bid for a second term look doubtful until his decision in early December to proceed with a run.

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Gray has not been charged and has denied wrongdoing. The federal investigation has resulted in guilty pleas from four campaign associates to various felony charges stemming from schemes that prosecutors say violated campaign finance laws.

Those “shortcomings,” Gray said Saturday, “caused many people great pain.”

“I know that our city suffered embarrassment,” he continued. “I want to apologize for the pain that my campaign — my campaign — caused, and I want to ask you for your forgiveness.”

The apology came three days after Gray first made a show of public remorse in a televised interview with WUSA-TV. He repeated several of the same rhetorical points Saturday, saying he could not “apologize for the misdeeds of others” but was sorry for the “pain and embarrassment” the wrongdoing caused.

Yet the mea culpa came with an edge, as Gray accused journalists and political opponents of playing up past misdeeds to distract attention from his administration’s accomplishments.

“I know that some reporters prefer a circus to a thoughtful discussion of issues,” he said. “I know that they care about ratings and selling newspapers. I care about you.”

After leaving the stage Saturday, Gray waded through a crushing crowd of supporters at the Town Hall Education Arts Recreation Campus, sharing handshakes and hugs but no comments for gathered reporters.

Gray will face as many as eight challengers in the April 1 Democratic primary. They include four D.C. Council members — Muriel Bowser (Ward 4), Jack Evans (Ward 2), Vincent B. Orange (At Large) and Tommy Wells (Ward 6) — as well as a former State Department official, Reta Jo Lewis, and restaurant owner and activist Andy Shallal.

Shallal, the owner of Busboys and Poets, drew some of the race’s first star power Saturday with a fundraiser at his Northwest Washington home with friend and actor Danny Glover.

Glover introduced Shallal, saying his campaign’s focus on erasing inequality could give the District a voice in a widening national discussion about priorities for the liberal left — not to mention, he said, a multicultural first family for the District.

“Imagine,” Glover said, to applause, “an Iraqi mayor and an Iranian first lady – it’s local politics, it’s national politics and world politics.”

On the day of Gray’s apologetic campaign kickoff, Shallal also said the city would be best served by a mayor with no reason for apologies:

“I’m the only candidate in this race who is not tainted by the pay-to-play culture that is pervasive in city hall. Nobody’s paid, nobody’s played with me,” Shallal said.

Gray’s speech did not announce any new initiatives but promised continued progress on existing ones. After touting his work on education and jobs, he addressed anxieties about the city’s growth and the rising cost of living, a leitmotif in many candidates’ campaign messaging this year.

He spoke of his affordable-housing efforts — an issue that got short shrift in his previous campaign, which focused on jobs, fiscal issues and ethics — and spoke of keeping housing costs affordable for longtime residents.

“Those are the folks who sacrificed and faced the challenges when, frankly, a lot of folks fled,” Gray said. “We cannot forget those who held our city together. They should not feel fear that soon a home in our city will be entirely out of their reach.”

He also played up his efforts to keep the District government open during the two-week federal shutdown in October: “I stood up to Congress and was able to say no to leaders on Capitol Hill because the 646,000 people who live here have my back,” he said. “And please know that I have your back, too.”

Supporters differed on whether Gray’s apology was necessary.

Carolyn Lynch, a 69-year-old resident of the Benning neighborhood, said she did not need to hear Gray apologize. “He is not responsible for what has gone on out of his earshot,” the retired District government employee said. “I think he is sorry that some of the people he trusted proved not to be trustworthy. . . . The turnout today proves that lot of people still support him.”

Sheila White, a Northeast resident, said it was “time to move on.”

“Instead of the $600,000, let’s look at what the U.S. attorney’s office has spent on this investigation,” she said, in a reference to the unreported “shadow campaign” spending that prosecutors say was funded by a major city contractor.

But Andre Lee, a 57-year-old Woodridge resident, said he was glad Gray tendered the mea culpa to supporters who worked honestly on his behalf in 2010 and saw their efforts clouded by the revelations of wrongdoing.

Lee is the political chairman for the AFSCME District Council 20, a government employees union that is strongly backing Gray. Lee said he also hoped the apology would refocus attention on the city’s progress in recent years.

“People are getting jobs; you’re bringing in businesses,” Lee said. “He’s making that happen.”

On Saturday, Gray introduced three new campaign co-chairs alongside Moore, who in his remarks ran through a litany of Gray administration accomplishments in economic development and other areas.

The co-chairs are Judith Terra, a philanthropist who supported Gray during his 2010 run; Sonia Gutierrez, the founder of a Columbia Heights charter school; and John Tinpe, a Burmese American restaurateur.

In the evening, Gray was scheduled to attend his first fundraiser, a closed-door affair at Terra’s home in Crestwood.

Among the most crucial early challenges for Gray will be raising sufficient cash to compete with his challengers, several of whom have been running for six months or longer and have raised hundreds of thousands of dollars.

The campaign’s fundraising efforts started coming together Wednesday, when a group of well-connected and well-heeled civic leaders gathered at the offices of lobbyist David Carmen.

A goal of collecting as much as $1 million by month’s end was discussed, according to three people in attendance who spoke on the condition of anonymity.

Campaign manager Chuck Thies, who spoke at the meeting, on Friday dismissed that figure, but he said a significant bankroll will be necessary.

“I sought to inspire the people there to get down to business,” he said. “In order for us to do the things we want to do, we want to have the resources to do them.”

Aaron C. Davis contributed to this report.