President Trump's former political challenger Chris Christie says that the president lacked the know-how of dealing with Democrats and proper negotiation skills when it came to handling the partial government shutdown, which ended after a record 35 days. The former New Jersey governor, in an interview with CBSN, said that while Mr. Trump's background in real estate is a "great career," it's "not really a preparation for the intricacies of government."

"I think what happened during the shutdown is an example of when -- where you don't have the experience of knowing how to deal with people in the other party, how legislative party works, what's important in terms of negotiating your way into those things and out of those things, we wind up with the longest shutdown in American history," Christie said.

He added, "That doesn't serve anybody well. That doesn't serve the president well. That doesn't the country well."

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The shutdown, which stemmed from debate over funding for the president's long-promised border wall with Mexico, came to a close after Mr. Trump on Friday agreed to end the shutdown for three weeks. Mr. Trump noted that he had the opportunity to declare a national emergency to build the wall but decided not to do so at this time, leaving many to question the president's next steps.

Christie said using executive authority to declare a national emergency in order to get the funding needed for a border wall is a "very dubious idea" and the "wrong thing to do."

"I don't think it would be upheld by the courts. And so when he's asked me my opinion for that, I've given it to him, which is 'be very careful.' Because when you use executive authority in a way that the courts strike down, you diminish the power of the presidency."

Meanwhile, as more Democrats and now third-party candidates step forward as a challenge to Mr. Trump in the 2020 race, Christie said he can't imagine a scenario in which anybody, including himself, could successfully take on the president.

"I think he'll be the nominee. And he'll have a tough race like he had a tough race in 2016. But no, I can't imagine that," Christie said when asked about his intentions to run for president.

The 2016 candidate, however, didn't completely rule out ever running again.

"I think the fact is I ran in 2016. I'm not saying I'd never run again. I'm 56 years old and you never know where life is going to take you and I don't have an interest in running for any other job."

CBS News' Erica D'Costa contributed to this report.