With 30 days to go until the mayoral primary, all four Democratic candidates and the man they hope to unseat braved the intense heat yesterday to march in the annual Dominican Day parade, to shake hands with potential voters, and to exchange political barbs before the clock runs out and city residents cast their ballots.

The parade topped off a long weekend of campaign appearances at subway stops, boardwalk festivals, churches, city pools, and news conferences, where, with a dwindling number of weekends left until Primary Day, the candidates moved into the homestretch of a race that has yet to enliven the electorate.

The Democratic front-runner, Fernando Ferrer, sought to enliven some of his supporters by denouncing Mayor Bloomberg for neglecting low- and middle-income residents.

He likened his own campaign to the biblical battle between David and Goliath.

The other three Democrats vying for the party’s nomination ratcheted up their attacks yesterday as well, assailing the mayor for everything from failing to garner enough federal homeland security money to posting campaign placards on police barricades.

Despite the attacks, there was no rain on Mr. Bloomberg’s Dominican Day parade. At the corner of 36th Street and Sixth Avenue in Manhattan, just before the parade started, Mr. Bloomberg, who is enjoying his best numbers in public opinion polls, declared: “Today all of us, by act of the mayor, are a little bit Dominican!”

And though the mayor looked composed as he marched up the Avenue of the Americas, at 59th Street, perhaps because the heat was wearing on him, he snapped at one of his press aides for a minor mix-up over the logistics of a planned stop at the edge of Central Park, telling the woman she wasn’t doing her job.

As the Bloomberg campaign bus blared music and a crowd of people waved Spanish-language Bloomberg campaign signs, the mayor finished the parade with a half-soaked shirt and with supporters chanting “Cuatro anos mas.”

The mayor even walked about 10 blocks of the parade route alongside a sometime critic, Reverend Al Sharpton, who has yet to endorse one of the Democrats, and whose presence next to him could give him a boost with African-American voters.

A few minutes before the parade started, one of those Democrats said Mr. Bloomberg should demand federal reimbursement for the roughly $2 million the city is spending in terrorism-related overtime pay for police officers. During a news conference at the entrance to the Lexington Avenue subway line at Grand Central Terminal, the speaker of the City Council, Gifford Miller, said that he supported the random bag searches the New York Police Department is conducting in subways, but that the city needs to do more to beef up security.

“Since New York’s security against terror is really the nation’s security against terror, Mayor Bloomberg should demand his fellow Republican George Bush reimburse us for these costs,” Mr. Miller said.

A half-hour later, when a reporter asked Mr. Bloomberg about Mr. Miller’s demand, the mayor said safety must come before money.

“I just think that we’ve got to make sure that we do what we have to do, regardless of who pays,” he said. “Remember what I said was that this city was going to do everything it can to keep the public safe and then we’ll go look for money.”

At times, yesterday’s Dominican Day parade seemed more like a candidates’ forum, with participation not only by the mayoral wannabes but also by candidates for public advocate, president of Manhattan, Manhattan district attorney, and other offices.

While the candidates squeezed in as much face time as they could with voters, they have also been using direct mail and commercials to increase their name recognition and get out their messages, unfiltered.

Messrs. Ferrer and Miller already have television commercials showing. The two other Democrats, the president of Manhattan, C. Virginia Fields, and a Brooklyn-Queens congressman, Anthony Weiner, plan to launch theirs closer to the September 13 primary.

Mr. Bloomberg, a billionaire who is financing his campaign with his personal fortune and is not accepting public matching money, has already outspent all of them combined.

His latest mailing is a four-page glossy brochure that was deposited in mailboxes over the weekend. In it, the mayor takes credit for creating 62,000 new jobs, giving homeowners a $400 property tax rebate, and eliminating the city sales tax on clothing ahead of schedule.

Mr. Bloomberg was criticized by his opponents for a similar radio advertisement that ran last month on 1010 WINS, but his campaign spokesman, Stuart Loeser, said yesterday the mayor had done the right thing by collecting more in taxes when the city was in financial despair and returning money to the people when the city recovered.

To the mayor’s leading opponent, however, the city has a long way to go until all of its residents reap the benefits of the economic rebound.

Mr. Ferrer spent his morning at the Brown Memorial Baptist Church in Brooklyn, where he wove a David-and-Goliath narrative for the congregation, casting himself in the role of the Judean king and urging New Yorkers to rise up and overwhelm their Philistine warrior mayor.

Addressing a sparse and almost entirely black congregation, Mr. Ferrer excoriated the mayor for having “next to nothing to say” about dropout rates in city schools, unemployment among the city’s black and Hispanic men, and the availability of “affordable housing.”

Mr. Ferrer said he was running for mayor because he understood the difficulties faced by New Yorkers struggling to make ends meet.

“I’m here because I was there,” the former Bronx president said. Of his chances for besting Mr. Bloomberg, Mr. Ferrer said: “I know what you’re thinking. This guy is a very wealthy guy.”

Waxing scriptural before the congregants, Mr. Ferrer then compared his campaign struggle against Mr. Bloomberg to the Old Testament’s best-known underdog tale.

Mr. Ferrer trails Mr. Bloomberg by 16 percentage points in the latest Quinnipiac University poll and has amassed $5 million in his war chest, compared to the $100 million Mr. Bloomberg is expected to spend on the election.

“You know, it’s not unlike that story in the Bible,” Mr. Ferrer said.

“A very big guy, the meanest guy in the valley comes in, in shining armor. … All the smart money was on Goliath. All the Philistines were on the sidelines, putting down bets,” Mr. Ferrer said, referring to the Aegean tribes who, in an almost constant state of war with the Israelites, enjoyed great power but ultimately went down to defeat at the hands of King David.

Later in the day, a spokeswoman for Mr. Ferrer, Christy Setzer, clarified his statements, saying he did not intend to characterize Mr. Bloomberg’s supporters as Philistines.

“The comparison is just about who the smart money’s on, and the smarter money was on David,” Ms. Setzer said.

Mr. Ferrer continued: “Some guy shows up, a champion of the other side – about my height, about my size, a small guy. No shining armor, no big, rippling muscles, no guys on the sidelines putting down bets.”

Ms. Setzer said Mr. Ferrer measures around 5 feet 10 inches in height. Mr. Bloomberg is 5 feet 7 inches tall.

Mr. Ferrer then recounted how, according to the biblical tale, “divine Providence” provided David with a staff, a slingshot, and “smooth stones” to battle Goliath, who was armed with sword and shield. “And the rest is history,” he said.

In the account of the struggle in 1 Samuel, David, using the slingshot, downs Goliath by embedding one of the smooth stones in his foe’s forehead. David then seizes the incapacitated Goliath’s sword and uses it to behead the warrior.

“Let us be the smooth stones,” Mr. Ferrer urged the congregants. “Let us overwhelm the guy with all the height and the shining armor. Let us prove that this is our city.”

Mr. Ferrer, who was greeted tepidly when he began his remarks, received enthusiastic applause when he concluded.

Mr. Loeser, the mayor’s campaign spokesman, responded: “If Freddy’s saying that it’s going to be tough running against a mayor who has brought crime down to record lows, led New York City through tough times by creating jobs and building housing, and started to reform a school system that politicians had always turned their backs on, then we aren’t going to argue with him.”

Mr. Ferrer was welcomed to the Brooklyn church by its pastor, Reverend Clinton Miller, who introduced the Democrat by first lambasting Mr. Bloomberg and deriding the mayor’s use of random bag searches in the subways as a means of thwarting terrorist attacks.

“The way to stop terror is to have a just foreign policy around the world,” Rev. Miller said, informing the congregants that “we are in a mess overseas” regarding the conflict in the Middle East, and that “we are in a mess at home” as well. Mr. Ferrer, too, addressed the war in Iraq, asking the congregation to join him in praying for the wife of a soldier dispatched there yesterday.

He also urged them to pray “for the informing of the minds of the people who’ve made him answer that call by issuing the call themselves, and for the inspiration of their hearts, that they will only make a call like that when it is absolutely necessary to do that.”