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'Genuinely friends': How Cory Booker and Andrew Yang bonded in competition

(CNN) New Jersey Sen. Cory Booker wasn't on the debate stage in California last week, but he did have a friend there.

Businessman Andrew Yang used a question about being the only candidate of color on the stage to tell America that he "missed Cory" and then he made a prediction: "I think Cory will be back."

It was a human moment during an otherwise antagonistic debate, and it earned Yang, who has fashioned himself the nice guy in the presidential race, a hearty round of applause and an appreciative text from Booker, who, according to a source, thanked Yang and said he hoped to prove his prediction right.

His response also highlighted something deeper: An unexpected but honest friendship between the two presidential candidates, one who has failed to live up to expectations and another who has surpassed his. Yang and Booker have known each other for years, aides say, but their relationship has deepened as they crisscross the country -- often times at the same events -- to vie for the chance to take on President Donald Trump in 2020.

"I like nice people. He's a really good guy," Booker told CNN on Friday. "He's just a nice human being who cares."

Politicians refer to their opponents as "my friend" so often that it has become a cliché. But in the case of Yang and Booker, it's sincere.

"I am genuinely friends with Cory," Yang told CNN after the debate. "We text each other. I miss the guy."

Yang was nonplussed about the moment after the debate, telling CNN it was "just a very natural thing for me to do" to someone who he thinks "will be back" on the stage soon.

That rapport has been on display throughout the campaign -- especially recently as the pressure put on candidates has increased.

When Yang was doing an interview with Macey, a young reporter from "The Ellen Degeneres Show," Booker jumped in and gave the businessman such a big hug that the senator picked him up in the air.

"I just want to give him a hug, if I can," Booker said.

When Macey tried to ask the two for the first thing they would do as president, Booker turned back to his friend.

"Well, if I'm president, one of the things I am going to do is invite him over for dinner," Booker said.

Days earlier, Yang ended a press conference he was holding by announcing the next candidate slated to speak.

"Ladies and gentlemen, Mr. Cory Booker," he shouted, sounding like a hype-man for the senator.

"That's like the days when your opening act is much bigger than the person who is doing the concert," said Booker.

"That's very, very kind, brother," Yang added. "I've looked up to this man for a long time, and it's a privilege to consider you a friend."

And the rapport has played out on Twitter, where Yang has turned his run-ins with Booker into a pseudo-running series, including a moment where -- according to a Booker staffer -- the New Jersey senator tried to speak with people while Yang stood behind him for about a minute tapping him on the shoulder repeatedly until Booker turned around.

Booker's reaction was to wrap Yang in a bear hug.

"I'm glad he's in this experience as well," Booker said Friday. "Andrew doesn't take himself too seriously. He is who he is."

He added: "I love when I see people in this race who are authentic."