Originally Published: 02 JAN 24 22:26 ET

Updated: 03 JAN 24 10:33 ET

By Alison Main, CNN

(CNN) — Republican presidential candidate Chris Christie on Tuesday pushed back on New Hampshire Gov. Chris Sununu’s recent suggestion that his campaign has no path forward.

“Since Chris started to work for Nikki Haley and become an employee of Nikki Haley, it’s not the same Chris Sununu anymore,” Christie, who has been friends with Sununu for more than a decade, told CNN’s Anderson Cooper on “AC360.”

“Chris Sununu was one of the most vocal Donald Trump critics in this country,” he said, later adding, “This is a guy who has said that Donald Trump is unfit. All things that his candidate is unwilling to say” and accusing Sununu of abandoning “his principles to try to get himself some political favor inside of his own state.”

The comments from Christie come as GOP presidential hopefuls seek to distinguish themselves in the final weeks before the Iowa caucuses. On Sunday, Sununu, who has endorsed former South Carolina Gov. Nikki Haley in the Republican primary, suggested the former New Jersey governor’s White House bid had reached a “dead end” and that he should drop it.

Christie told Cooper that he thinks Sununu chose to endorse Haley “based on a set of polling at that moment,” asking: “What indications does he have that she wants to beat Donald Trump?”

“By the way, how does Chris Sununu defend what she said on Civil War? I don’t understand it,” he continued, leaning into criticism of Haley’s failure to mention slavery as a cause of the Civil War at a New Hampshire town hall and subsequent effort to clean up her answer.

Sununu responded to Christie’s criticism on CNN on Wednesday morning, saying, “Chris is a good guy. He’s a smart guy. He’s working hard. I get it, he’s frustrated.”

“Chris knows when he got into the race it was a long shot…for all of them, it really was. Everyone knew we had to consolidate around one candidate. Chris has done a very good job speaking the truth on Trump, as a lot of us have,” he said.

CNN has reached out to Haley’s campaign for comment.

The New Hampshire Republican, who chose to forgo a presidential bid himself, said Christie has an opportunity to “be a hero” to “not just bow out gracefully, but help consolidate this race.”

He said the goal is not to have Christie’s current poll numbers get any higher to “be the difference make and allow Trump to win.”

Responding to criticism that Haley and other candidates aren’t doing enough to take on Trump directly, Sununu denied that Haley should shift her strategy on that point.

“Of all the candidates, even with Trump, she’s the only one with momentum, right?,” he said, pointing out that Trump, though he’s the “standard bearer of the party” has the support of just over 40% of Republican primary voters in New Hampshire.

Earlier Tuesday, Sunnu said “Chris has kind of hit his limit, if you will” and that he “speaks the truth on Trump, but that’s very different than whether it translates into votes for a nomination to become president of the United States.”

“I’m not telling Chris that he has to get out, right?” Sununu said following a Haley campaign event in Rye, New Hampshire. “I’m not calling Chris Christie and saying you absolutely have to get out. I think he’s just smart enough to see the writing on the wall to know that he has a great opportunity here not just to get behind Nikki, but to do something really important for the country and the party and start moving us forward.”

In his interview with Cooper, Christie also weighed in on the GOP front-runner, saying he thinks the US Supreme Court would dismiss “really quickly” Trump’s argument that he has immunity from federal prosecution for alleged crimes he committed while in office – a fundamental issue in the special counsel’s 2020 election subversion criminal case against the former president.

Pressed on whether he believes the high court will take up the case, Christie said he thinks the justices may “give it the back of their hand” and “say forget it and go with the lower court rulings.”

“I just don’t believe that there’s any real argument,” he said. “Think about the practicality of it. That a president could literally do anything. And if he wasn’t impeached and removed for it, he escapes all type of criminal or civil legal liability. It doesn’t make any sense.”

CNN’s Ebony Davis contributed to this report.