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Christie: Trump 'hurts the credibility of the presidency'

New Jersey Gov. Chris Christie speaks at the Northeast Republican Leadership Conference in Philadelphia, June 19, 2015. (Photo by Matt Rourke/AP)
New Jersey Gov. Chris Christie speaks at the Northeast Republican Leadership Conference in Philadelphia, June 19, 2015. 

New Jersey Gov. Chris Christie’s declaration that he’s done talking about his GOP presidential competitor Donald Trump certainly didn’t last long.

The governor swiped at the billionaire real estate mogul during an interview with CNBC on Tuesday, arguing that Trump hurts the credibility of the presidency.

“I think it’s much less likely for him to be successful than it is for me to be successful. I don’t think it’s in the best interests of your party to have someone who I don’t think would be an effective president to be the nominee. But in the end, that’s why I’m running,” said Christie, who was campaigning in the early voting state of New Hampshire.

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The governor specifically criticized Trump’s “great line” about building a wall at the border between the U.S. and Mexico and somehow getting the Mexican government to pay for it.

“When you do that, it hurts the credibility of the presidency. You have to have some experience in [the] actual difficulty of governing ... You need to understand how you have to work with other people, how if you disagree with someone, you can’t just fire them,” said Christie.

Until now, Christie has treaded lightly when speaking about Trump, who he has called a friend. But Trump — who has been at the top of polls even after making controversial remarks about undocumented immigrants and Sen. John McCain’s war record — is seemingly becoming impossible to ignore.

Christie has said more than once this month that he’s done taking questions about Trump, and instead wants to focus on bigger problems the country is facing. The governor has also argued “nobody in the real world” asks him about the reality star.

But in Keene, New Hampshire, on Monday, Christie was confronted by a pro-Trump supporter who wanted to know why she should back the governor for president instead of Trump. Christie argued Trump’s business skills were not “transferrable.”

During the CNBC interview, Christie was asked about Trump’s criticism of his proposal to overhaul social security. Trump has insisted he’ll make the country so rich that such drastic moves aren’t necessary.

RELATED: Chris Christie to receive 2016 endorsement from Maryland governor

“That math doesn’t support Donald’s position,” the governor said. “ Listen, my proposal is substantive and based upon the facts on the ground of social security. This is not just about growth, although growth is very important to every element of our economy and I have a plan to deal with growth, but you still have to deal with the facts.”

According to a Monmouth University poll released on Tuesday, Trump holds a significant lead among likely New Hampshire Republican presidential primary voters. Almost one-quarter — 24% — said they backed Trump while former Florida Gov. Jeb Bush came in second with 12%.

Christie came in sixth place with 4% support, but fell within the poll’s margin of error of plus or minus 4.5 percentage points — in striking distance of Ohio Gov. John Kasich and Wisconsin Gov. Scott Walker, who both received 7%; Sen. Marco Rubio of Florida, who earned 6%; and retired neurosurgeon Ben Carson and Sen. Rand Paul of Kentucky, who both got 5%.