Former New Jersey Gov. Chris Christie, who is seriously considering a 2024 presidential campaign, told Axios that he will never support Donald Trump for president again — even if he wins the Republican nomination.

Why it matters: No potential GOP candidate has made such an explicit pledge, underscoring the degree to which Christie is betting on the viability of an anti-Trump lane in the primary.

The big picture: Christie was one of the first top Republicans to back Trump in 2016 after the reality TV star emerged as the front-runner in the presidential race — and even helped the former president prepare to debate Joe Biden during the 2020 campaign.

• If Christie gets in the race, he is prepared to play the role of anti-Trump prosecutor at a time when Trump's other Republican rivals have been reticent to go after him directly.
• Christie previewed his line of attack in a speech Monday at St. Anselm College in New Hampshire, where he said Republicans need someone to take down Trump on the debate stage the way he viciously took down Sen. Marco Rubio (R-Fla.) in 2016.

What they're saying: "I'm going to go out there and tell the truth. Like the truth matters. The truth is not negotiable," Christie told Axios.

• Asked whether he'd support Trump as the GOP nominee in 2024, Christie said: "I can't help him. No way."
• "Look, I just can't," Christie went on. "When you have the Jan. 6 choir at a rally and you show video of it — I just don't think that person is appropriate for the presidency."
• Christie said he wouldn't be voting for Biden, either. "I can't imagine myself voting for Joe Biden, either. I don't know if I can vote for either of these guys. They're both too old. They're both out of touch with what's going on in the world right now."

Between the lines: "Look, what I thought in 2016 was that [Trump] going to be the nominee, and I don't want Hillary Clinton to be the president," Christie said about his past support for Trump, which lasted until the Jan. 6 Capitol attack.

• "Did I have concerns about him? Of course, but you probably have concerns about any candidate other than yourself in the end."