The papers filed on January 8 are the first official step towards a run for the seat in 2014.
There had been speculation that Booker might challenge Governor Chris Christie this year, but in December he announced his intentions to consider a run for Senate.
It is unclear if Booker would be challenging five-term Sen. Frank Lautenberg, who has yet to announce his intentions. Lautenberg at 88 is the oldest member of the Senate.
The Stanford-educated Booker has steadily built his national profile over the last six years as Newark's mayor. An adept social media user with 1.3 million Twitter followers, Booker is known for responding to constituent complaints electronically and last year took on a tweeted challenge to live on food stamps for a week.
Lautenberg, who was treated for cancer three years ago, missed the Jan. 1 vote on the "fiscal cliff" legislation because of the flu but has never given any indication that he would like to retire.
And Booker has not said whether he would be willing to take on Lautenberg in a primary run if the senator tries to keep his seat.
In 2008, New Jersey's Democratic establishment decided that Lautenberg was not too old to serve.
U.S. Rep. Rob Andrews challenged him a primary. Most of the state's Democratic leaders stood with Lautenberg, who won handily then retained his seat in the general election.
U.S. Rep. Frank Pallone, a Democrat from central New Jersey, has also expressed interest in Lautenberg's seat. But on Friday, his spokesman, Raymond Zaccaro, said Pallone's not thinking about whether he'll run in the election, which is 22 months away, but instead is focused solely on recovery from Superstorm Sandy, which hit his district hard.
Booker was elected mayor of Newark in 2006 with 72 percent of the vote, four years after narrowly losing a bruising battle against longtime Mayor Sharpe James. The race was chronicled in the 2005 documentary "Street Fight." He was re-elected in 2010 with about 60 percent of the vote.
During Superstorm Sandy, he invited residents to charge their cellphones at his house. In April, he let the world know through Twitter that he rushed into his neighbor's house and rescued her from a fire. During a snowstorm, he helped shovel people out.
Booker's critics say he spends too much time rubbing elbows with celebrities and not enough fixing his city.
But in one case, his high-profile connections paid off. In 2010, after sitting with Booker at a dinner, Facebook founder Mark Zuckerberg agreed to donate $100 million to try to improve education in the city. Booker also boasts of a more stable city budget and of downtown redevelopment on his watch.
A Rhodes Scholar who grew up in suburban Harrington Park, N.J., Booker is the son of civil rights activists who were among the first black executives at IBM. He got his law degree from Yale Law School, then moved to one of Newark's most notoriously violent housing projects.
Some information from The Associated Press
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