Another speaker likened Vice President Kamala Harris to a prostitute with “pimp handlers.” A third called her “the Antichrist.” And the former Fox News host Tucker Carlson mocked Ms. Harris — the daughter of an Indian mother and a Jamaican father — with a made-up ethnicity, saying she was vying to become “the first Samoan-Malaysian, low IQ former California prosecutor ever to be elected president.”

By the time the former president himself took the stage, an event billed as delivering the closing message of his campaign, with nine days left in a tossup race, had instead become a carnival of grievances, misogyny and racism.

If the parade of speakers felt at times like a Republican National Convention reunion — Senator JD Vance of Ohio, Mr. Carlson, Vivek Ramaswamy, Alina Habba, Lee Greenwood, the Trump family all appeared — they seemed to have returned for a bonus fifth night that was more inflammatory than the original in July.

The rally served as a capstone to an escalating series of remarks from Mr. Trump, who has repeatedly said in recent days that one of the gravest threats that America faces is “the enemy within.” Democrats have cranked up warnings of Mr. Trump’s descent into authoritarianism as John F. Kelly, the former Marine general who was his longest-serving chief of staff, warned that Mr. Trump met the definition of a fascist.

“When I say ‘the enemy from within,’ the other side goes crazy,” Mr. Trump said on Sunday, mocking his critics.

Since early in his campaign, he has broadly promised an era of “retribution” if he wins. But after a relative lull earlier this year, he has grown more specific of late, including promising prosecutions against a variety of people if they’re deemed to have “cheated” in the election and to fire the special counsel, Jack Smith, who brought two federal indictments against him, and even suggesting throwing him out of the country entirely.

On Sunday, Mr. Trump described the date of his potential election as a “liberation day” from what he described as an occupation by invading migrants.

Ms. Harris’s campaign seized on the spectacle, and some Republicans, including from Florida and Puerto Rico, denounced the comic’s comments about the island. Several influential Puerto Rican superstars, Bad Bunny, Jennifer Lopez, Luis Fonsi and Ricky Martin, lent their voice for Ms. Harris on Sunday.

But Mr. Trump has paid little political price over time for his own inflammatory remarks in the past — he has disparaged cities with large Black populations such as Detroit and Milwaukee this year — let alone those of his surrogates and supporters.

The marathon of speeches — Mr. Trump took the stage two hours after scheduled — was often infused with more self-indulgence than political strategy. Mr. Trump plainly enjoyed playing the Garden, which bills itself as “the world’s most famous arena.”

“Kamala, you’re fired!” Mr. Trump said, returning to the line that he first made famous as host of “The Apprentice.”

But he went so long that the crowd had begun to thin noticeably before he had finished his 78-minute speech.

The event was a spectacle that captured the unusual and sometimes ugly range of the MAGA movement that has taken over the Republican Party from the inside over the last nine years.

Hulk Hogan flexed his muscles and ripped off his clothes, just as he did at the convention. Donald Trump Jr. called his father a “badass.” The world’s richest man, Elon Musk, who has poured $118 million of his fortune to aid Mr. Trump so far, entered to a video of his rocket booster landing, pumping his fists in the air. He promptly predicted the federal budget could be slashed by one-third even as Mr. Trump rolled out deficit-expanding tax breaks.

Stephen Miller, a senior Trump adviser who influenced Mr. Trump’s anti-immigrant crackdown, used nativist language as he argued that only Mr. Trump would stand up and say “America is for Americans and Americans only.”

The big surprise was a rare public speech by Melania Trump, who introduced her husband and exited the stage with him after he had finished, as the Village People’s “Y.M.C.A.” blared.

The arrival of thousands of red hats at the symbolic arena at the center of a blue city in a blue state was celebrated by Trump supporters who relished the chance to collectively thumb their noses at the New York and national elite.

“Selling out the Garden means the MAGA movement has now arrived,” Jack Posobiec, the right-wing activist with a big following on social media, said in an interview. “It’s Madison Square Garden, it’s the center of everything, and to have this place filled with MAGA hats and Trump supporters really goes to show you it’s not just the surprise win of 2016 — it’s a nationwide movement.”

It was lost on no one that Mr. Trump was just miles from where he was convicted of 34 felony counts earlier this year and still awaiting sentencing, and a short jaunt to Trump Tower, where he opened his first presidential campaign in 2015.

The singular nature of Mr. Trump’s candidacy was emblazoned in slogan form on the scoreboard above as he began to speak: “Trump will fix it.”

Mr. Trump opened by asking the crowd a timeworn political line: “Are you better off now than you were four years ago?” It is at the core of Mr. Trump’s campaign against Ms. Harris ever since she replaced President Biden, a switch he remains sore about. Despite being delivered in a city that four years ago was the epicenter of the coronavirus pandemic and still deep in shutdowns and closed businesses, and swimming in a high death toll, that line landed well.

Mr. Trump’s vows of mass deportation and inveighing against undocumented immigrants had an audience in New York City, too, where thousands of migrants who crossed the southern border without authorization have been given sanctuary and some residents have complained about the use of city services to help them.

So many of the day’s warm-up speeches were spent portraying the former president as he wants to be seen. Several speakers talked about him surviving a July assassination attempt not in spiritual terms but in muscular ones, describing his toughness at “dodging” the bullet. Many also falsely claimed he “built” the skyline in a city in which he was always seen as a B-list developer with a small portfolio of buildings that he acquired long after they were constructed.

“The king of New York is back to reclaim the city that he built,” his son, Donald Trump Jr., declared anyway.

The elder Mr. Trump, who normally speaks only glowingly about his late father, Fred, from whom he inherited millions of dollars and the spine of his real-estate company, delivered a surprising line about his parents as he reflected on how they would be receiving word of his legal travails.

“I know my mother’s in heaven, I’m not 100 percent sure about my father, but it’s close,” Mr. Trump said, to laughter in the arena.

It was all a surreal scene.

At one point, the painter Scott LoBaido received a huge cheer when he flipped a middle finger to the crowd before grabbing a paintbrush to paint an American flag as “America the Beautiful” boomed. The grand finale was revealing an image of Mr. Trump hugging the Empire State Building.

Later, the television host Phil McGraw, known as Dr. Phil, lectured the crowd on why Mr. Trump did not fit the definition of “a bully” because a bully requires “an imbalance of power,” seeming to ignore the fact that Mr. Trump has enormous power as a billionaire and former president.

During the speech by Mr. Trump’s running mate, Mr. Vance, the entire arena spontaneously burst into chants of “Tampon Tim” to disparage Gov. Tim Walz of Minnesota, Ms. Harris’s running mate.

“You all can say that,” Mr. Vance smiled. “I probably shouldn’t say that.”

It was a rare moment of restraint at the microphone.

David Rem, a childhood friend of Mr. Trump, called Ms. Harris “the devil.” Grant Cardone, a businessman, declared that the sitting vice president had “pimp handlers.” Sid Rosenberg denounced Hillary Clinton as a “sick son of a bitch” for linking the Trump rally and a pro-Nazi event at the arena of the same name decades ago.

Mr. Rosenberg called the entire Democratic Party “a bunch of degenerates, lowlives, Jew-haters and lowlives. Every one of them.”

When the comedian Tony Hinchcliffe made his remark about Puerto Rico, there were groans from many in the audience.

On the same afternoon, Ms. Harris was in Philadelphia, courting Pennsylvania’s significant Latino population and stopping by Freddy & Tony’s, a Puerto Rican restaurant.

“Timing is everything,” David Plouffe, a top Harris adviser, wrote on X, posting clips of the two side-by-side.

In his White House bid, Mr. Trump has banked on winning uncommon shares of Black and Latino voters, in part by leaning into culture wars that split the Democratic Party.

In his speech, Robert F. Kennedy Jr. invoked his uncle, former Senator Ted Kennedy, for creating Title IX for women’s sports. He used that heritage to defend his own current opposition to transgender women participating in sports.

Mr. Carlson marveled aloud from the stage at following the party-switching Mr. Kennedy. “It’s a realignment,” he declared. “It’s unbelievable.”

Twenty years ago, in the same arena, Rudolph W. Giuliani delivered the keynote address at the 2004 Republican National Convention, three years after the Sept. 11 terrorist attack prompted then-President George W. Bush to caution the nation against hate.

On Sunday, Mr. Giuliani leaned into overbroad stereotyping against the Palestinian people, who he said “are taught to kill us at two years old.”

“I don’t take a risk with people that are taught to kill Americans at 2,” he said. “I’m on the side of Israel.”

Mr. Giuliani praised Mr. Trump for coming to the city where he once served as Republican mayor.

“This is where a Republican is not supposed to come,” Mr. Giuliani said. “Which is why Donald Trump came here.”

The remarks at the rally came as Ms. Harris wrapped up a day in Philadelphia, where she spent time courting Pennsylvania’s significant Puerto Rican population by visiting a local Puerto Rican restaurant. While there, she talked about a new plan she announced on Sunday to bring economic opportunities to Puerto Rico, discussed her visit there after Hurricane Maria, and said that even as a senator she had “felt a need and an obligation” to “make sure Puerto Rico’s needs were met.”

“This is not a new area of focus for me,” she said. She received a warm reception from the crowd, with chants of “Sí, se puede.”

Before the Trump rally on Sunday, Ms. Harris had already taken aim at her Republican rival in a video message to Puerto Rican voters. She noted that, as president, Mr. Trump had resisted sending aid to the island after back-to-back hurricanes, adding that he had offered nothing but “paper towels and insults.”

“I will never forget what Donald Trump did and what he did not do when Puerto Rico needed a caring and a competent leader,” she said.

The video was widely shared, and the Puerto Rican superstar Bad Bunny posted it on Instagram. He is one of the biggest recording artists in the world and among the most influential Latino artists. Other celebrities with Puerto Rican backgrounds also shared the video, including Jennifer Lopez and Ricky Martin.

“Quite a split screen,” Kevin Munoz, a Harris campaign spokesman, said in a statement, calling the offensive language at the Trump rally “no surprise.” The campaign also sent out a news release titled “All the Crazy Things (So Far) at Trump’s ‘Closing Argument’ Madison Square Garden Rally.”

The Trump campaign appeared wary of the political fallout from the “island of garbage” remark and other comments. A senior adviser, Danielle Alvarez, said in a statement, “This joke does not reflect the views of President Trump or the campaign.”

Fresh off a blitz of star-studded rallies, Ms. Harris focused on retail politicking in Philadelphia on Sunday as her campaign makes its final push to mobilize working-class communities and people of color to the polls.

In neighborhoods across the city, Ms. Harris delivered tailored messages to different groups of voters as she continued her effort to secure the crucial “blue wall” states of Pennsylvania, Michigan and Wisconsin. It was Ms. Harris’s 14th visit to Pennsylvania since she became the Democratic presidential nominee, and her seventh to the Philadelphia area.

“Victory runs through Philly,” she said while visiting a Black bookstore, Hakim’s Bookstore and Gift Shop. “It runs through Pennsylvania.”

Ms. Harris started the day at a predominantly Black church, where she warned parishioners that “these next nine days will test us,” and brought them to their feet when she told them, “We were born for a time such as this.”

At a barbershop, Philly Cuts, she talked about the need to recruit and retain more Black male teachers, which was part of an economic agenda her campaign unveiled this month that was targeted at Black men. Ms. Harris spent an hour at the barbershop speaking with several Black men, and was invited to sit in a “magical” chair at the back of the shop; the barbers said every candidate running for elected office who had sat in the chair had won her or his election.

Darryl Thomas, 52, the owner of Philly Cuts, said that Ms. Harris had spent much of the time discussing what Black men were looking for from their next president. He said that she had “good dialogue” with the group.

“Black males are the most disenfranchised individuals in America,” he said. “This is a time when the playing field needs to be leveled and fair. We’re not asking for extras.”

Ms. Harris ended her day with a get-out-the-vote rally at a community center, during which she told energetic supporters they had the “power” to make their voices heard at the ballot box.

“There is too much on the line, and we must not wake up the day after the election and have any regrets about what we could have done in these next nine days,” she said. “So let’s spend these next nine days knowing we did everything we could.”

Mattathias Schwartz , Jazmine Ulloa and Katie Rogers contributed reporting.