While some GOP presidential candidates continue to crisscross the country, making speeches and looking to generate support, New Jersey Governor Chris Christie has spent almost all of his time campaigning in New Hampshire, where the first primary will be held in a couple of months.

This coming weekend, Christie will begin a 3-day bus tour of the Granite state.

So why is he doing this?

According to Rider University political science professor Ben Dworkin, it’s really the only choice Christie has had.

He points out after the Bridgegate scandal came to light almost two years ago Christie’s approval numbers plummeted, in Jersey and across the country, and it dramatically slowed the momentum he had coming off of a huge re-election victory in 2013 — so he decided to hyper-focus on New Hampshire “in order to get him ingrained with the people there. He’s been very personal, texting local leaders, calling people, cultivating people.

And lately, those efforts have paid off.

“Those negatives that he had have dropped,” Dworki said, “And his overall approval and the people who are ready to support him in New Hampshire has moved up."

He stresses this turn of events was very important because earlier this week it allowed him to participate in the main GOP debate.

“New Hampshire is critical to the Chris Christie presidential campaign. Not only does he have to do well, he has to do extremely well,” Dworkin said. “He needs to be the No. 1 candidate behind Donald Trump, and for now I think we can assume Donald Trump is going to win, given his current strength.”

If that happens, Dworkin said, “he wins press attention and the focus of the party leadership to say, hey maybe this is the guy, someone we can rally around if we want to avoid having Trump. To come in fourth or fifth place is not going to cut it for Christie. Given the amount of time and resources he’s put into New Hampshire, he really needs to win or come in second.”

He points out that kind of showing could propel the Christie campaign forward to South Carolina and Nevada, the next primary voting states.

“If he doesn’t do well in New Hampshire,” Dworkin said, “then I’m not sure how much longer the campaign will be able to go.”

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