Newark, N.J., Mayor Cory Booker, a national political star considered the Democrat with the best chance to defeat Gov. Christie, won't run against the popular Republican next year - but may run for the U.S. Senate in 2014.

Booker's announcement, delivered Thursday morning via Twitter and a web video after months of speculation, alters the state's political landscape and leaves a host of questions about other Democrats who may seek Christie's job.

It also means that Christie's path to reelection is considerably less complicated.

So far, the only prominent Democrat who has said publicly she will take on Christie is State Sen. Barbara Buono of Middlesex County, who does not as of now have the fund-raising prowess, name recognition, or favorability ratings of Booker or Christie.

Booker's announcement was branded with the Twitter hashtag #finishingthework to indicate that he will remain in Newark for the two years left in his second mayoral term.

In the accompanying video on CoryBooker.com, he listed his accomplishments in Newark, then added: "As for my political future, I will explore the possibility of running for the U.S. Senate in 2014."

That seat is held by Sen. Frank J. Lautenberg, an 88-year-old Democrat who - if he chooses not to retire - would be Booker's opponent in a primary. Lautenberg has been circumspect about his plans, but political observers note that if he runs, he will be seeking a term that would end when he was 96.

Lautenberg's spokesman issued a statement Thursday saying the senator was "focused on passing a critical disaster relief bill for New Jersey and addressing America's broken gun laws. . . . This is not the time for political distractions and the senator will address politics next year."

If Booker became the Democrats' senatorial candidate, his path to victory would be easier than if he faced Christie for the governorship. Christie's favorability ratings since Sandy have been in the 70 percent range - and the Garden State has elected nothing but Democrats to the Senate for 40 years. Four Republicans have made it to the governor's chair in that time.

"There's no question [Booker] chose the easier race," said Brigid Harrison, a political science professor at Montclair State University. "Though I would argue that if he were to run and win for governor, it would have propelled him much quicker into the national spotlight and real leadership capacity."

A Christie-Booker race would have garnered nationwide attention because Christie, 50, is considered a 2016 presidential contender and because Booker is the state's most prominent Democrat.

Booker's personal story and dynamic speaking style have attracted him support from Hollywood to Wall Street. He's just 43, but he has been the subject of both a documentary about his unsuccessful run for mayor in 2002 and a Sundance Channel series looking at his work leading Newark.

A Rhodes scholar and child of the suburbs who lived in the projects in his adopted hometown after graduation from Yale Law School, Booker is famous for shaking off his security detail to save a neighbor from her burning home in April. He has 1.3 million Twitter followers, more than almost any politician who has not run for president, and uses social media to serve up spiritual quotations and respond to constituent complaints.

During Sandy, Booker let constituents without power stay at his home, and this month made several cable TV appearances to talk about his week living on the budget of a food stamp recipient.

"Booker was the biggest impediment to [Christie's] election bid," Harrison said. "I would imagine they are probably celebrating in the governor's office."

Buono does not have Booker's star power. But while Booker is a friend of Christie's and has stood beside him, literally, for some of the governor's biggest political initiatives, Buono's liberal voting record contrasts sharply with Christie's positions.

With Booker out, other Democrats will consider entering the race. The most formidable would be State Sen. Richard Codey (D., Essex), who became governor after Gov. Jim McGreevey resigned and who still uses the honorific title. In an interview Thursday, Codey said he would decide within two weeks whether to run.

Asked about Christie's approval ratings, Codey said the numbers would likely fall back to earth: "I'm the greatest example of [the adage]: 'One day in politics is a lifetime.' "

In South Jersey, Senate President Stephen Sweeney (D., Gloucester) and Assembly Majority Leader Lou Greenwald (D., Camden) were said to be mulling gubernatorial candidacies in recent months. But sources now say it is unlikely they would pass up running for reelection for their legislative seats in order to pursue the governorship. Both are positioned to have leadership positions in the legislature for years to come.

Other Democrats rumored to be thinking about running are Elizabeth Mayor Chris Bollwage and U.S. Rep. Bill Pascrell, who represents North Jersey.

Booker's decision reflects a change of heart. In 2010, according to the Newark Star-Ledger, he said when asked about serving in the Senate: "I can think of no office that would be less attractive. I would be discussing rules of procedure until I'm nauseous."

Contact Matt Katz

at 609-217-8355 or mkatz@phillynews.com, or follow on Twitter @mattkatz00. Read his blog, "Christie Chronicles," at www.philly.com/christie

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