Allies of former Gov. Chris Christie of New Jersey have formed a super PAC to support him in the nascent Republican primary, as he makes preparations for a likely campaign kickoff in the next two weeks, according to an official with the group and others briefed on the matter.

Mr. Christie’s candidacy is likely to to focus in part on drawing a stark contrast with former President Donald J. Trump. Mr. Christie supported Mr. Trump in 2016 and worked with him during his presidency, but they split over Mr. Trump’s claims on election night in 2020 that the race was stolen from him.

People who have been close to Mr. Christie for years are leading the outside group, Tell It Like It Is, which is laying the groundwork for an imminent announcement, one of the people briefed on the matter said. Brian Jones, an aide who advised Senator John McCain’s presidential bid in 2008 and Mitt Romney’s in 2012, will run the effort.

William P. Palatucci, a longtime adviser to Mr. Christie and a Republican National Committee member, will be the chair. Another long-serving adviser to Mr. Christie, Russ Schriefer, will oversee messaging as a senior adviser; and Brent Seaborn, a veteran data guru, will focus on voter targeting.

Maria Comella, an adviser who also was chief of staff to former Gov. Andrew Cuomo of New York, and Mike DuHaime, Mr. Christie’s top political strategist in 2016, are expected to run an eventual campaign if Mr. Christie announces as expected. Anthony Scaramucci, the hedge fund adviser who served for less than two weeks as a communications director in the Trump White House and has become a vocal Trump critic, has said he will support Mr. Christie if he runs.

Mr. Christie “is willing to confront the hard truths that currently threaten the future of the Republican Party,” Mr. Jones said in a statement. “Now more than ever we need leaders that have the courage to say not what we want to hear but what we need to hear.”

Mr. Christie has said recently that he would run if he believed he could win, but he had indicated that there were organizational issues he needed to figure out. The existence of the super PAC and the pending announcement suggest those issues have been resolved.

A Christie candidacy is seen as a long shot in a Republican Party that has been remade in Mr. Trump’s image eight years after Mr. Christie first ran for president. Mr. Trump vanquished him, and Mr. Christie dropped out after coming in sixth in New Hampshire, where he had staked his candidacy.

A central challenge of this campaign will be explaining to voters his transformation. He endorsed Mr. Trump in 2016, helped him with debate prep and acted at times as an informal adviser during his presidency. Then, in the earliest hours of Nov. 4, 2020, Mr. Christie split with him when he questioned Mr. Trump’s declaration that there had been widespread fraud in the election.

“We heard nothing today about any evidence,” Mr. Christie said in an appearance on ABC News. “This kind of thing, all it does is inflame without informing. And we cannot permit inflammation without information.”

Since then, Mr. Christie has become a full-throated critic of Mr. Trump, talking as a former federal prosecutor about the former president’s legal travails and describing him as a loser who can no longer command the crowds he once did. Mr. Christie’s candidacy is being watched by donors who either like what he’s saying or see him as the best opportunity to damage Mr. Trump, particularly from a debate stage.

And like some other candidates, such as former Vice President Mike Pence, Mr. Christie appears to be banking on the notion that there are enough vestiges of the old Republican Party to which he can appeal.

While New Hampshire is seen as a potentially favorable state where Mr. Christie could make inroads, his advisers are not expected to hang his candidacy on a specific state. Instead, he is expected to try to get as much media attention as possible with an unconventional campaign that will travel to places where his message is most appealing.

He will be coming into the 2024 race as the person with the most coherent case against Mr. Trump while arguing that the fight needs to be taken directly to the former president.

Mr. Christie is hoping to tamp down some of the grievance that has seeped into the roots of political discourse in the Republican Party since Mr. Trump became the party’s nominee in 2016. Mr. Christie is approaching the race, allies say, with the goal of delivering a hopeful message.

But Mr. Christie has also repeatedly taken shots at Gov. Ron DeSantis of Florida, the distant second to Mr. Trump in most public polls, describing Mr. DeSantis’s fight with Disney in particular as an overreach.

“Where are we headed here now that, if you express disagreement in this country, the government is allowed to punish you? To me, that’s what I always thought liberals did. And now all of a sudden here we are participating in this with a Republican governor,” Mr. Christie said last month.