Sen. Cory Booker (D-New Jersey) said Tuesday that there's no way Republican presidential candidate Donald Trump will be president.

While promoting his book, "United," during an interview with Business Insider on Tuesday, Booker predicted that Trump would not become the country's next president.

But he admitted that he was surprised Trump remains in a strong front-running position, following his disparaging remarks about Republicans like Sen. John McCain (R-Arizona).

"I don't think that's going to come to pass," Booker said of Trump. "I thought that Donald Trump's ascendancy would end when he attacked John McCain, saying he's not a war hero. I found that shocking, for him to say that."

"I've been wrong on everything about Trump, I've been wrong about everything on the Republican side of the ledger," he continued. "But allow me — with that caveat — to made the prediction that Donald Trump will not be the president of the United States. It just will not happen."

Booker said Trump's low popularity levels among different demographic groups outside of the Republican Party would make him weak in a general election.

"His approval ratings are below water on a lot of very important metrics in this country," Booker said. "I'm not sure if he can pull a nomination out."

The New Jersey senator, who is supporting former Secretary of State Hillary Clinton's presidential bid, did reserve some praise for Trump's family. Booker specifically lauded Trump's daughter, Ivanka, who was a campaign- fundraising "bundler" for Booker during his 2013 special-election Senate campaign.

"I know Donald Trump, I've met him, I know his family," Booker said. "I have love, and friendship, and affection for his family members. But I'm going to work very hard to ensure that he is not our president."

"Ivanka is a woman of great grace and kindness and has been a good friend to me," he added. "We attack each other so viciously in this political cycle, not knowing their heart, not knowing their character."