Then-New Jersey Gov. Chris Christie fields questions at a wide-ranging news conference, March 3, 2016, at the Statehouse in Trenton. (Getty Images)

Former New Jersey Gov. Chris Christie hasn’t ruled out challenging President Trump in 2020 as his scathing book indicting the administration nears release next week.

Christie, who ran for president 2016 but dropped out during the Republican primaries and went on to support Trump, spoke in Riverside County, Calif., this week at an event that was part of the Desert Town Hall Speakers Series.

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In recent weeks, ahead of his book release titled “Let Me Finish: Trump, The Kushners, Bannon, New Jersey and the Power of In-Your-Face Politics,” Christie has been making many public addresses, fueling speculation that he may challenge Trump in 2020.

“Never say never,” he told the audience in Indian Wells after being asked whether he will seek the White House, KESQ-TV of Palm Springs reported.

“Never say never.”
— Chris Christie on a possible 2020 presidential run

Christie went on to say that other candidates in the past, such as former President Ronald Reagan, suffered defeats before eventually winning.

“Once you’ve got this in your blood, it’s hard to get rid of it,” he said.

The former governor went from vicious opposition to Trump during the campaign -- calling him a potential “entertainer-in-chief” -- to being one of the leading surrogates for the president.

Following the election, he took a prominent position within Trump's transition team -- and many expected his support and loyalty for the president to be rewarded with a key role in the administration.

But as Christie’s new book details, the knives were out for him soon after he started leading the transition team, with Trump's son-in-law Jared Kushner engineering his ouster.

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Christie accused Kushner of executing revenge for his actions as a U.S. attorney for New Jersey in 2005 when he prosecuted Kushner’s father, Charles Kushner, for illegal campaign contributions, tax evasion and witness tampering. The father ended up serving 14 months in prison.

Christie also slammed the Trump administration for having a “revolving door of deeply flawed individuals — amateurs, grifters, weaklings, convicted and unconvicted felons — who were hustled into jobs they were never suited for, sometimes seemingly without so much as a background check via Google or Wikipedia."

At the same time, just days after Christie’s remarks, FBI Director Christopher Wray, who previously worked as Christie’s attorney before leading the bureau, released a video Friday saying he was “about as angry as I've been in a long, long time” over the partial government shutdown.

“Making some people stay home when they don't want to, and making others show up without pay -- it's mind-boggling, it's short-sighted, and it's unfair," Wray said.

“You know better than most that we've been thrust into the political spotlight more than we would have liked over the past few years,” Wray added. “And the last thing this organization needs now is its leadership to wade into the middle of a full-on political dispute.”

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But at the event on Tuesday, Christie also took a less critical approach than his subordinate. He said Trump “made the fundamental mistake” of telling House Speaker Nancy Pelosi and Senate Majority Leader Chuck Schumer that we will “own the shutdown” of the federal government even before it happened.

The government was reopened on Friday after Trump signed a short-term spending bill, ending the longest partial federal government shutdown in U.S. history. Trump signed the stop-gap plan just hours after the measure passed the Senate and House, respectively.