Chris Christie, one of GOP's loudest anti-Trump voices, files paperwork for presidential bid

Former New Jersey Gov. Chris Christie is set to launch his presidential campaign on Tuesday night, joining a crowded -- and still growing -- GOP primary field.

Christie will announce his bid at a town hall-style event in New Hampshire, a key early primary state. The event is being hosted by the New Hampshire Institute of Politics outside Manchester.

Earlier on Tuesday, Christie filed his campaign paperwork with the Federal Election Commission.

He will be joining a field that is currently led by former President Donald Trump and Florida Gov. Ron DeSantis. Other primary contenders include former South Carolina Gov. Nikki Haley, South Carolina Sen. Tim Scott, former Arkansas Gov. Asa Hutchinson and tech entrepreneur Vivek Ramaswamy.

Former Vice President Mike Pence and North Dakota Gov. Doug Burgum are anticipated to launch their own campaigns on Wednesday.

Christie will have significant ground to make up, as early polls compiled by FiveThirtyEight show him in the single digits, badly trailing both Trump and DeSantis.

A Monmouth University poll released last week also showed Christie's favorability rating among Republican voters deeply underwater, with just 21% viewing him favorably and 47% viewing him unfavorably.

A political group backing Trump on Tuesday argued that Christie's entry shows how the field is fracturing -- as, they insist, Trump's support consolidates against Florida Gov. Ron Desantis, his main rival.

"President Trump's dominance over the Republican primary field has opened a mad rush to seize the mantle for runner-up. Ron DeSantis is not ready for this moment, and Chris Christie will waste no time eating DeSantis' lunch," Karoline Leavitt, a spokeswoman for Make America Great Again Inc., said in a statement, in part.

Christie's campaign, which is expected to feature a sprawling offensive against Trump, marks a full-circle moment for the former governor, who quickly endorsed Trump after dropping out of the 2016 presidential race and largely remained a vocal ally during Trump's four years in the White House.

However, Christie broke with Trump over the Jan. 6, 2021, insurrection and has remained one of his loudest critics within the GOP, including as a then-ABC News contributor frequently appearing on programs like "This Week."

Christie has lamented what he views as a lack of candidates in the GOP field who can adequately attack Trump head-on. He has frequently cited one 2016 debate in which he lambasted Sen. Marco Rubio, R-Fla., for giving canned answers -- barbs that many believe helped sink Rubio's bid.

"You better have somebody on that stage who can do to him what I did to Marco, because that's the only thing that's gonna defeat Donald Trump," Christie said earlier this year.

Still, he insisted he wouldn't join the race just to take on Trump if he didn't see a path for himself, saying he's "not a paid assassin."

He is also anticipated to campaign heavily in New Hampshire, given the state's independent streak and history of electing Republicans seen as more centrist -- where Christie's more anti-Trump message may resonate over deep-red states like Iowa and South Carolina, which also hold early nominating contests next year.

ABC News' Nicholas Kerr contributed to this report.