Chris Christie: I need to get to work in Iowa, NH

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Gov. Chris Christie said Monday he's disappointed he won't be on the main stage in the next GOP presidential debate, but stressed the real work is on the ground in the first-in-the-nation primary contests of Iowa and New Hampshire.

"I have to get to work," Christie said in a CNBC "Squawk Box" interview. "What's sustained is the foundation you're laying in the two early states."

The New Jersey governor did not meet the 2.5 percent average support threshold in national polls needed for the prime-time debate on Tuesday night in Milwaukee hosted by Fox Business News and The Wall Street Journal.

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He's going to be on the undercard debate earlier in the evening, along with former Sen. Rick Santorum, Louisiana Gov. Bobby Jindal, and former Arkansas Gov. Mike Huckabee, who was also relegated from the main stage for the first time.

"The debates are a moment in time, and if you look at people who've done well in the debates and I'm one of them ... according to [pundits]," Christie said, "it's kind of like a sugar high. You get a bump, and then a couple weeks later most of the bump goes away."

Christie said he's been "pleasantly surprised" that people who thought he got overlooked in the upcoming fourth debate have stepped up their donations to his campaign.

In contrast to last month's debate disappointment, Christie's campaign got a boost when a video of his impassioned comments to New Hampshire voters in early October about the demons of addiction went viral.

In the video recorded by the Huffington Post and posted late last month, Christie related personal stories about his late mother's smoking and a law school friend who became hooked on prescription painkillers. He also advocated treatment for nonviolent drug offenders, instead of prison.

"In a week, it's got 7.7 million views," Christie told CNBC on Monday. "I think that's what people want. They want somebody who's going to authentically and directly speak to the issues they care about."

In an interview a day after last month's CNBC debate, Christie told "Squawk Box" he's a battle-tested candidate who can take on Democratic front-runner Hillary Clinton and win the White House for Republicans.