Booker called Democratic party leaders Thursday morning to inform them of his plans, the Newark Star-Ledger reports.
Booker said earlier he was "absolutely considering" a gubernatorial run, calling Christie "vulnerable." Elizabeth, N.J. Mayor Chris Bollwage (D) told The Huffington Post Booker's past uncertainty on his future plans had "frozen" the state's Democratic Party.
Rep. Frank Pallone has also expressed interest in Lautenberg's seat.
UPDATE -- 11:35 a.m.: Booker said he'd explore a run for senate in an op-ed in the Newark Star-Ledger. Click here to read the op-ed.