"I will explore the possibility of running for the United States Senate in 2014," Booker said in the video.
A Booker ally familiar with the mayor's thinking added: "Those close to him believe he has made the decision to run for the Senate.”
Booker vowed to complete his term as mayor of Newark, meaning he won't be running for governor next year. He was elected to a second four-year term in 2010. The popular Democratic mayor had been considering both a run for governor and a bid for the Senate, indicating in recent interviews that he was zeroing in on a decision.
Much of Booker's three-and-a-half minute video is devoted to defending his record in Newark. A recent New York Times story explored the problems that have plagued the city under Booker's watch.
Booker's decision means Lautenberg's future will come under increased scrutiny. The longtime Democratic senator is up for reelection in 2014, but may opt for retirement. Lautenberg will turn 89 in January; he is the oldest member of the Senate.
A Lautenberg spokesman said in a Thursday statement that given the current issues the senator is dealing with, it's not a time for "political distractions," and Lautenberg will address his political future next year.
"Senator Lautenberg is focused on passing a critical disaster relief bill for New Jersey and addressing America's broken gun laws," said Lautenberg spokesman Caley Gray. "The last several months and weeks have been a painful time for New Jersey and America, and the Senator is working on the tough issues we face. This is not the time for political distractions and the Senator will address politics next year."
For his part, Booker said that he intends to consult with Lautenberg as he makes his final decision about a Senate run.
"I look forward to consulting with Sen. Frank Lautenberg. It would be a privilege and honor to continue his legacy of service," said Booker in his video.
Christie’s sky-high popularity and Booker’s own encouraging numbers as a potential Senate candidate may have moved the Democrat toward a Senate run. A recent survey from Democratic-leaning pollster Public Policy Polling showed that New Jersey Democratic voters prefer Booker over Lautenberg by a nearly 3-1 margin in 2014.
For Christie, Booker’s decision is welcome news. The rising Democratic star would have been the most formidable potential challenger against the incumbent, recent polling showed.
Christie has been riding a wave of popularity following his handling of Hurricane Sandy, which included a heavily scrutinized decision to invite President Obama to the Garden State to survey storm damage and meet with affected residents. Recent polling has pegged Christie’s approval rating to be as high as 77 percent in New Jersey.
With Booker out of the running in the governor's race, Democrats are left with an open field. Barbara Buono, a little-known state senator who recent polling showed was running behind Christie by as many as 40 points, is the only declared Democratic candidate. State Sen. and former governor Richard Codey, state Assemblyman Lou Greenwald, state Senate president Stephen Sweeney, Assembly Majority Leader Lou Greenwald, and Rep. Frank Pallone are among Democratic names being mentioned as possible contenders.
Christie announced late last month that he would run for a second term.
New Jersey is one of two states slated to hold gubernatorial elections in 2013. In Virginia, a high-profile showdown between state Attorney General Ken Cuccinelli III (R) and former Democratic National Committee chairman Terry McAuliffe appears to be in the offing.
Chris Cillizza contributed to this post
Updated at 3:49 p.m.