Christie, a former Trump ally turned critic who sought to position himself as the only Republican contender willing to go toe-to-toe with the pugnacious former president, had been seen as a longshot for the party's nomination.
Since launching his bid in June, Christie has been a staple on cable news shows offering withering critiques of Trump, calling him unfit for office and arguing that he was morally responsible for the Jan. 6, 2021, attack the U.S. Capitol.
While the broadsides earned Christie a sliver of support among Republicans wanting to move in a new direction, Trump's tight grip on the party's most active members meant Christie never rose above low single digits in national polls.
His departure eliminates the most vocal Trump antagonist from the race, although Nikki Haley, the former governor of South Carolina and former U.S. ambassador to the United Nations, has grown increasingly critical of Trump in recent months.
Christie, 61, has repeatedly predicted that Trump would likely lose in the general election to Democratic President Joe Biden, given the four criminal cases hanging over the former president's candidacy.
Christie ran for president in 2016 but ended his bid after a disappointing finish in the New Hampshire primary and became the first major party figure to back Trump. He helped run Trump's debate preparations in 2020 but disavowed the former president following his false claims that he won the 2020 election.
(Reporting by Nathan Layne in Wilton, Connecticut, editing by Ross Colvin and Alistair Bell)
