Former New Jersey Gov. Chris Christie is expected to announce his 2024 presidential run on Tuesday, joining a growing field of Republican candidates trying to wrestle GOP power away from former President Donald Trump.

Christie, 60, has a complicated relationship with Trump. He endorsed the former president after his own failed run in 2016, and despite not landing in a cabinet position in the Trump administration, as many speculated he would, Christie again endorsed Trump in 2020. But in recent years he's sounded like anything but a friend of Trump's, posting numerous anti-Trump tweets and mocking the former president's defiant posture before his New York indictment as "baloney."

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Certain aspects of Christie and Trump's partnership have always seemed uncomfortable. At Trump's Super Tuesday victory speech during the 2016 primaries, Christie's strained onstage expression became a national talking point and meme, with some likening Christie to a "hostage" and others regarding him as a reluctant lackey. Christie denied any discomfort and said the commentary came from "armchair psychiatrists."

At the time, although Trump was popular with Republican voters, many in the party establishment still viewed him as a divisive, wildcard outsider. His provocative style, inflammatory statements and downplaying of problematic incidents from his past all stood out as liabilities to the GOP's reputation.

Even in the weeks before the 2016 election, when key Republican skeptics had embraced Trump as an alternative to Hillary Clinton, the leaking of the 2005 "Access Hollywood" tape put Trump in a light that made the GOP appear indifferent, at best, to a leader making such crude, misogynistic remarks.

Christie, then a friend and advisor to Trump, called that leaked video "hard to watch" in his 2019 memoir. But under the political circumstances, he still felt Trump's "locker room talk" description of the taped conversation with Billy Bush was the "best" response Trump could have given in his public apology. 

And while Trump did go on to win that election, it's still the case that heading into the 2024 race, he's in the news most often these days for being the first U.S. president to be indicted for alleged criminal activity. Trump has not exactly demonstrated that the original concerns of Republicans were unfounded.

Republican candidates have widely emulated Trump and invoked his influence in the years since his presidency. Christie, however, has attempted to fashion himself as a different type of Republican — one wise to the realities of the Trump-era GOP, but grounded in the party's traditional values.

After the 2016 election, Christie claimed he was offered seven different positions in the Trump administration but turned down all of them. He said his support for Trump was not conditional on a job and that he was only interested in being either Trump's vice president or attorney general, neither of which were on the table.

"I'm not desperate for a title. I'm not looking to run to Washington, D.C," Christie told CNBC in 2019. "What I'm looking to do is to make the country better and to help my friend."

There have been other theories and rumors about why Christie never became a part of Trump's cabinet. Animosity between Christie and Trump's inner circle, including Steve Bannon and Jared Kushner, have been among the explanations. Christie's connection to the infamous "Bridgegate" scandal in New Jersey, also may have dimmed his appeal for high-level positions. Christie claimed his wife's wish to avoid a move to D.C. was his primary motivation for not taking other White House roles. 

But Christie, who took a job as political contributor for ABC News after finishing his second term as New Jersey governor in January 2018, hasn't held his tongue on his opinion of the Trump administration, describing it as "riffraff" and the people in it as "greedy," "inexperienced," and "not ready for prime time."

Lately, Christie has been negatively tweeting about Trump concerning issues like illegal immigration and the war in Ukraine, even calling Trump a "coward" and a "puppet of (Vladimir) Putin" during a radio appearance last month.

Christie's allegiance to Trump started to publicly unravel after Joe Biden's election victory in 2020, as Trump spread false claims of voter fraud with strident public statements and dozens of lawsuits that were repeatedly shot down by state and federal courts. Trump's relentless conspiracies about a stolen election helped fuel the mob of his supporters who stormed the U.S. Capitol on Jan. 6.

As a former federal prosecutor, Christie claimed he couldn't stomach Trump's refusal to accept losing the election. During a 2021 appearance on the podcast of CNN political commentator David Axelrod, formerly a senior advisor to Barack Obama, Christie explained why he distanced himself from Trump.

"The red line was election night, David," Christie said. "Standing behind the seal of the president and saying the election was stolen, and then offering not one piece of evidence to support that."

Christie said he would have supported Trump's fight if there had been legitimate evidence to back up his claims, but the insistent lying put the country at risk.

"When you put yourself ahead of our democracy as president of the United States, it's over," Christie said this March during a speech at St. Anselm College in New Hampshire, where he's expected to announce his 2024 run on Tuesday.

He told audience members at the March event that his past support for Trump was "a strategic error" motivated by opposition to the Democratic candidates, and that he couldn't have predicted the kind of president Trump would be.

Christie joins a growing field of Republicans hoping to become president in 2024, including Florida Gov. Ron DeSantis, South Carolina Rep. Tim Scott, former U.N. Ambassador Nikki Haley and former Arkansas Gov. Asa Hutchinson. Former Vice President Mike Pencefiled his campaign paperwork on Monday, officially becoming a candidate, too. 

Trump announced his 2024 presidential campaign in November, before he was indicted in a federal case about his alleged role in a hush-money payment made to porn star Stormy Daniels in 2016. The former president could be facing additional prosecution in other investigations, as well, including one for the potential mishandling of classified documents that were kept at his home in Mar-a-Lago and another regarding whether he broke the law while attempting to overturn Georgia's 2020 election results.

In Christie's 2021 book, "Republican Rescue: Saving the Party From Truth Deniers, Conspiracy Theorists, and the Dangerous Policies of Joe Biden," the Newark, New Jersey native laid out his case for the GOP to depart from Trump's brash brand of personality-driven politics and the right-wing fringes it has embraced.

But Christie has a confrontational streak of his own that surfaced during town halls and other events, including when he was finishing up his second term as New Jersey governor and launching his 2016 presidential campaign.

When hecklers disrupted a 2014 town hall promoting his budget, Christie snapped that they should "Sit down and keep quiet."

"Some days I sit and listen and take it and give a reasonable answer in response and sometimes if I'm in a cranky mood I yell back, and you've all seen this," Christie said about getting flak from people who attended his public appearances while he was governor.

At a presidential campaign event in 2015, Christie had a testy exchange with a man who questioned his record on gun ownership, since New Jersey has some of the strictest laws in the country. Christie repeatedly challenged the man to provide even "one fact" that he's anti-gun, calling the questioner's point of view "dead wrong."

And at another event in New Hampshire in early 2016, a woman asked Christie why he wasn't in New Jersey and present for the cleanup of damage caused by a severe winter storm. "Do you want me to go down there with a mop?" said Christie, who had remained New Jersey's governor while running for president.

Plans for another presidential run, first reported by Axios, include Christie pitching himself to the "exhausted majority" of American voters and taking on Trump during the buildup to 2024. A Monmouth University poll released last week, examining the 10 current and potential 2024 GOP presidential candidates, had Christie as the only one to be rated negatively by Republican voters. 

Given his history with Trump, Christie has no other choice but to battle him on the campaign trail. If Christie sticks around in the race, this could become one of the ugliest — and most engrossing — storylines of the Republican presidential primaries in the coming year. 

For Trump, a public fight with Chris Christie — a man who once stood by his side, only to change his tune years later — could give him an easy target during primary season. Christie may be confident that he's a worthy adversary for Trump, but he will need considerably more support from Republican voters to level the playing field.