Booker's tweet linked to a statement on his website in which he writes, "Let there be no doubt, I will complete my full second term as mayor. As for my political future, I will explore the possibility of running for The United States Senate in 2014."
Sources tell Eyewitness News reporter Dave Evans that Booker will only run if Lautenberg declines. Lautenberg will be 90 in 2014.
"As I explore a run for the United States Senate, I look forward to consulting with Senator Lautenberg," he wrote in his statement. "During my lifetime, he has been one of New Jersey's most important leaders. It would be a privilege to continue his great legacy of service."
The decision means that Booker will not be challenging Governor Chris Christie next year. Booker was considered the best chance for Democrats against the popular Republican governor.
Booker reached out to Lautenberg on Thursday morning, but it's not clear whether the two talked. Booker also made a round of calls to Democratic county political chairs and state Senate President Stephen Sweeney, another Democrat said to be considering a run for governor or another office.
"It will be a privilege, an honor, to continue his legacy of service," Booker said of Lautenberg in a 3-minute video that accompanied his announcement. Booker was not available for questions.
Many Democrats viewed Booker as having the best chance at unseating Christie, a Republican. One Democrat, state Sen. Barbara Buono of Metuchen, has announced a gubernatorial candidacy so far. Now that Booker's out, the party will look for decisions from others including Sweeney and Sen. Dick Codey.
Christie's popularity is at an all-time high following his handling of Hurricane Sandy and its aftermath. In announcing his re-election bid last month, Christie said he was motivated, in part, by the chance to lead New Jersey through the post-storm recovery, which he said won't be complete when his first term expires.
Booker and Christie historically have had a good working relationship. They agreed on the elimination of lifetime teacher tenure, for example, and on the need for government workers to pay more for their retirement and health benefits. The two even appeared in a "Seinfeld" parody video this year.
But Newark schools remain under state control and the city relies on the Christie administration for millions in aid to make up its deficit. As Booker eyed a gubernatorial run more publicly, Christie ramped up criticism of the mayor's fiscal management.
Critics say the celebrity mayor is much more popular beyond the city's borders than within Newark. Former Gov. Brendan Byrne, a fellow Democrat, cast doubt on Booker's ability to be as an effective an administrator as the governorship requires.
There is little doubt that Booker can raise money, however. He has brought in hundreds of millions in development and donations to the city, including a $100 million education donation from Facebook founder Mark Zuckerberg.
In the video, he touted other achievements of his administration, including more budget stability, court reforms and a reduction in crime.
"Amazingly, in a down economy, Newark is in its biggest period of economic growth since the 1950s," he said.
Despite the development and philanthropic money, Newark's unemployment rate stands at about 15 percent and the city continues to rely on the state to help balance the budget. The city council did not pass the 2012 budget until October. The state lent Newark $32 million last year, and it ended up with an $18 million surplus. So this year, Christie slashed the aid by $22 million, chiding the administration for how it handled the budget.
Booker has 1.3 million Twitter followers and is known for responding to constituent complaints sent to him electronically. 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. And during a snowstorm, he helped shovel people out.
He 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 A Stanford-educated 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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