Newark Mayor Cory Booker announced Thursday that he plans to explore a possible bid for Senate in 2014, effectively ruling out a run against Republican New Jersey Gov. Chris Christie. 

Booker revealed his plans in a web video posted late Thursday morning. In it, he vowed to complete his full second term as mayor, and added: "I will explore the possibility of running for the United States Senate in 2014." 

The seat up in 2014 is currently held by Democrat Frank Lautenberg. There's no word on whether Lautenberg will retire. Lautenberg is 88. Booker is 43. 

Booker was seen as the Democrats' best chance for taking on Christie in 2013, with both of them having emerged as national political figures. However, the Republican governor's approval ratings have been on the rise in the wake of Superstorm Sandy. 

In announcing his own bid for re-election 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.

Now that Booker's out, the party will look for decisions from others including state Senate President Stephen Sweeney and Sen. Dick Codey. 

The Associated Press contributed to this report.