Booker was joined at the news conference by former U.S. Sen. Bill Bradley, a former pro basketball player who for 18 years held the Senate seat Booker is seeking.
Bradley called Booker “the right person for the right office at the right time.”
Booker started fundraising for a 2014 Senate campaign after announcing he would not run against Christie for governor, citing his desire to finish his term in Newark, which expires in June 2014.
On Saturday, he said he would be sad to leave Newark sooner than planned. But he expressed confidence that $1 billion in development projects in the pipeline would move forward and that the city’s momentum would continue. He said his to-do list before leaving includes continuing to increase transparency and accountability in the city police department and to leave a funding mechanism for hiring police every year.
Booker is considered the early front-runner, though election observers agree anything can happen in a hastily called summer election.
Pallone, 61, has deep union ties. Holt, 64, a former research physicist, has $800,000 on hand.
A Democratic party official in northern New Jersey sued Friday to try to get the special election held Nov. 5, the same date Christie is up for re-election.
The winner of the October special election will hold the seat until November 2014, when voters will elect a senator for the regular six-year term.
Booker pledged not to run a negative campaign against Holt, who he’s fund-raised for previously, or Pallone, who has been in Congress since 1993. All three are known to support liberal causes.
Booker has 1.4 million followers on Twitter — or five for every resident of the city where he’s the mayor. He tweets frequently, answering questions about city services, posting about his workouts and, perhaps most often, trying to provide inspiration.
He’s frequently gotten public attention, from staging a hunger strike to protest drug-dealing to rescuing a woman from a burning home last year. His life story is also captivating. He grew up in Harrington Park as the son of civil rights activists who were among the first black executives at IBM, went to Stanford, was a Rhodes Scholar, earned a law degree from Yale and took a job with the Urban Justice Center, which provides legal and other services to the vulnerable. He also moved to a public housing complex in Newark.
Booker’s critics in Newark see him as an ambitious interloper who spends too much of his time outside the city.
In 2010, he was seated next to Facebook founder Mark Zuckerberg at a dinner during a conference in Sun Valley, Idaho. Two months later, Zuckerberg announced a $100 million donation to improve education in Newark. Zuckerberg is planning to host a fundraiser for Booker’s Senate run soon.
Associated Press writers Geoff Mulvihill and Katie Zezima in Newark contributed to this story.