The former New Jersey Governor was picked up on a hot mic Wednesday ahead of announcing he's pulling out of the presidential race ... talking to someone about who can potentially hold their own in the primaries.

You can hear him say, "She's gonna get smoked" and "She's not up to this," referring to Haley.

This was Christie's 2nd attempt at the White House. BTW -- he went up against Donald Trump in 2016, but pulled out after his approval rating was simply anemic.

This time around, he went up against Trump, Haley, Ron DeSantis and Vivek Ramaswamy -- and things got heated between the candidates on the debate floor.

Vivek fat-shamed CC in December, shutting him down on the topic of foreign policy by saying, "Just walk yourself off that stage, enjoy a nice meal, and get the hell out of this race."

While Trump was absent from all debates, Christie let him have it nonetheless -- calling him Donald Duck, citing how often the former President was "ducking" the debates.