Earlier in the day Booker, in a separate interview with CNN, said Christie is "vulnerable" to a strong reelection challenge.

"Christie is vulnerable, as it should be, because there's a lot of issues in the state he's not falling in line with," Booker said. "From women's issues, environmental issues, from really going in a balanced way."

In the same CNN interview Booker said his thinking on whether to run, and where, was about where he could make the most impact.

"I'm putting a lot of people I trust around me, trying to make the decision based simply on this: where I think I can make the most difference in the city I love and the state I love and the nation I pledged my life to," Booker said.