Chris Christie on Wednesday slammed his Republican presidential opponent Vivek Ramaswamy for vocally supporting Donald Trump.

During an August primary debate, Ramaswamy had accused Christie of running a campaign based on “vengeance and grievance” against the former president, who is likewise seeking the GOP nomination. In a new interview with Fox News, Christie was asked about that claim and his frequent comments about Trump.

“How do you run against someone and not talk about them?” replied Christie, a onetime governor of New Jersey.

“I look at what Vivek does here — he’s practically his [Trump’s] wingman. And he says he’s the greatest president of the 21st century. Well, if he is, what the hell are you doing running? You should just drop out and endorse Donald Trump for reelection, which I think is essentially what he’s doing,” he added. “I think he’s auditioning for a Cabinet position if Donald Trump were ever to become president again.”

At the same August debate, Ramaswamy not only called Trump the “best president of the 21st century,” but vowed to pardon the former president — who currently faces four criminal indictments — if he wins the election.

Trump subsequently praised Ramaswamy as a “very, very, very intelligent person” and said he’d consider the biotech entrepreneur as a running mate.

Ramaswamy has claimed he’s not interested in the gig.

In September, when a Fox News host asked what the point of his campaign is if he’s not willing to accept a vice presidency, the upstart candidate said he wants to take Trump’s “America First agenda even further” and “I can’t do that from a number-two position or a Cabinet role.”

Still, Ramaswamy has made headlines for occasional criticism of the former president. Last month, he said Trump had made a “false promise” about repealing the Affordable Care Act health care law. And he has blasted Trump’s actions around efforts to overturn the 2020 election results. But he has also ducked questions about such remarks.

Trump is far and away the front-runner in the GOP race. Ramaswamy is polling on average at about 7.3%, while Christie is at 2.7%, according to FiveThirtyEight.

Watch Christie’s Fox News interview below.