How and Why Chris Christie Endorsed Donald Trump

— -- The timing could not have been better -– but it was a lucky accident for a campaign that’s in control of the presidential race.

Gov. Chris Christie decided to endorse Donald Trump Thursday afternoon, hours before the debate in Houston that saw Trump come under harsh attack by Marco Rubio, according to an adviser who spoke on condition of anonymity.

Christie had a secret meeting at Trump Tower in Manhattan that morning, and told aides of his decision around 5 p.m. Thursday. He told them he was headed to Texas to make his endorsement, setting off a wild 24 hours capped by a joint Christie-Trump appearance in Fort Worth.

Trump introduced the New Jersey governor as a "real standout."

“He has been a spectacular governor. He has been just a wonderful person and a wonderful loyal person,” Trump said ahead of his rally.

According to the adviser, Christie, during his campaign, grew frustrated that so many donors and elected officials were sitting out the primary battle. He decided when he exited the race after the New Hampshire primary that he wouldn’t wait too long to endorse if it became obvious who the nominee would be.

“Why would I be any better if I was on the sidelines,” was his thinking, the adviser said.

Christie feels that Trump is overwhelmingly likely to be the nominee. He has respect for Ohio Gov. John Kasich, but sees no realistic path for him to the nomination. As for Ted Cruz and Marco Rubio, he would support either if he became the nominee, but there was “zero chance” he’d go for a first-term senator if given a choice in the matter, the adviser said.

After proudly endorsing Trump, Christie said that the New York real estate mogul will “provide strong, unequivocal leadership” and would “undoubtedly” be the best candidate to beat “Hillary Clinton in November.

“They [Democrats] do not know the playbook with Donald Trump because he is rewriting the playbook. He is rewriting playbook of American politics because he is providing strong leadership that is not dependent upon the status quo," Christie said.

This adviser stressed a 14-year relationship between Christie and Trump, although it’s mostly a social one. Also, there are obvious stylistic similarities, and Christie respects Trump -- notwithstanding the nasty things he said about him -- as a leader and as an executive.

He also has seen, over time, a kind of quiet establishment comfort with Trump -– in New Jersey and among other friends, including big-money people in the party and also regular people he interacts with. Christie respects the way the party has begun to coalesce around Trump despite not having elected officials or a traditional advertising strategy.

The decision gave Trump perhaps his biggest endorsement to date -– a boost well-timed to take a bigger lead in the race for the GOP nomination.