'Donald Trump said he didn't expect to stay in race past Oct 2015'

New York: Donald Trump told New Jersey Governor Chris Christie just months after he launched his presidential campaign in June 2015 that he did not expect to stay in the race past October of that year, a new book claims.

Trump told Christie, who at that point was also running for president, that he "didn't expect to make it past October" and would endorse Christie when he dropped out, an unnamed Christie adviser said, according to a new book out by several members of CNN's political team.

"I think they always had an understanding that the first one out would probably endorse the other," the adviser was quoted as saying in the book, "Unprecedented: The Election that Changed Everything" that is scheduled to be released on December six.

During the throes of the Republican primary, Trump and Christie had a common enemy: Marco Rubio. After Christie's endorsement, Trump would praise Christie for his takedown of Rubio during the Republican debate right before the New Hampshire primary.

Christie mercilessly mocked Rubio when he repeated a talking point again and again to criticise President Barack Obama.

During the Republican primary, Christie and Trump -- who have known each other through New York-area politics -- were not as harsh toward each other as were other pairs of rivals.

Christie, though, did criticise Trump by calling on voters to get serious and not treat the election as a game, and Trump at one point alleged that Christie knew about his now-convicted aides' plans to close down the George Washington Bridge.

Christie has since become one of President-elect Trump's most stalwart defenders, and he is currently under consideration for a number of high-profile cabinet posts, CNN reported.

But on Friday, Christie was layered over as chair of Trump's transition team, with Trump's vice president, Mike Pence, now in charge of assembling the Trump administration.

The relationship between two outsized personalities will continue to unfold in the months ahead, the report said.