Mr. Christie needled his higher-polling rivals while campaigning in their home state of Florida.
If Gov. Ron DeSantis follows political consultants’ advice to defend former President Donald J. Trump during the first Republican presidential debate next week, then he should “get the hell out of the race,” former Gov. Chris Christie of New Jersey said on Friday, poking Mr. DeSantis from his home state of Florida.
“He should do Donald Trump a favor and do our party a favor, come back to Tallahassee and endorse Donald Trump,” Mr. Christie said to applause before a friendly crowd in South Miami. “The only way to beat someone,” he added, “is to beat him.”
Mr. Christie mocked a strategy memo, internal polling and other data published online by a firm associated with a super PAC that has effectively taken over Mr. DeSantis’s campaign. With unusual bluntness, the documents suggested that Mr. DeSantis defend Mr. Trump against Mr. Christie’s expected debate attacks. The documents advised Mr. DeSantis to credit Mr. Trump for his accomplishments, but add that it is time for a new standard-bearer.
Mr. Christie stepped up his criticisms of Mr. DeSantis in a pair of South Florida campaign appearances, as it seemed increasingly likely that he would not get the debate-stage confrontation with Mr. Trump he had been spoiling for — and that he would instead have to settle for the next highest-polling rival. Mr. DeSantis, though leading Mr. Christie and the rest of the field, has appeared weakened heading into Wednesday.
When asked by a reporter about the memo on Friday, Mr. Christie said the guidance showed that Mr. DeSantis lacked the authenticity and principles to be president.
“If you’re running for president of the United States, are you really going to let some other group of people tell you what to say?” he said. “This campaign of his has gone from up here to down here because people are really beginning to wonder what the hell he stands for.”
Mr. DeSantis has been cautious about upsetting Trump supporters for fear of alienating the Republican primary base, a strategy that has hampered the Florida governor’s ability to contrast himself with Mr. Trump, the party’s front-runner.
On Friday, over more than 90 minutes of remarks and answers to questions, sprinkled with colorful language and jokes, Mr. Christie repeatedly jabbed Mr. DeSantis and Mr. Trump, the two Floridians who have dominated the state’s politics and rarely faced criticism from anyone in their own party.
The receptive, bipartisan crowd sipping Cuban coffee and nibbling on pastries seemed a throwback to Republican politics before the Trump era.
One man, a self-described “liberal Democrat,” said he would be open to supporting Mr. Christie. Another woman who said she was a lifelong Democrat said that she was dissatisfied with her party’s direction and unhappy with the possibility of having to choose between Mr. Trump and President Biden again, an opinion shared by many voters on the campaign trail.
Mr. Christie, who trails Mr. Trump and Mr. DeSantis in the polls, said that was why he was “not conceding” the political conversation to his rivals.
“Some people would say, ‘Why bother coming to Florida if two of the other candidates already live here?'” Mr. Christie said. “I’m here because we need to talk about these things.”
At first, his criticism of Mr. DeSantis was indirect: He did not refer to Mr. DeSantis by name when he mentioned an opponent who had dismissed the war in Ukraine as a “territorial dispute.” (Mr. DeSantis later walked back that comment.) But then Mr. Christie brought up concerns about Mr. DeSantis’s zeal for divisive cultural issues involving transgender people and Disney.
“I don’t understand your governor,” he said, also name-checking Mr. Trump and Vivek Ramaswamy, another Republican presidential hopeful who has also campaigned against “woke” policies. “Maybe today you like what they’re going after, but tomorrow maybe they’re going to go after something you like.”
Later, Mr. Christie swung by Versailles, Miami’s famous Cuban restaurant and a frequent stop for politicians, where he did not order anything but instead worked the lunch crowd, shaking hands and posing for selfies, especially with tourists from New York, New Jersey and Philadelphia. “We’re having fun,” he told one group.
In a gaggle with reporters, Mr. Christie dismissed polls that showed negative ratings for him among Republican voters — “Those numbers change,” he said — as well as Mr. Trump’s rising popularity with the G.O.P. base after each of the four criminal indictments against him.
“Whether you believe what he did was criminal or not is much less important than the idea that the conduct is awful,” he said, “and beneath, in my view, the office of the president.”
Mr. Trump’s decision to skip the debate, he added, is insulting to voters.
“Not showing up is completely disrespectful to the Republican Party, who has made you their nominee twice,” he said.