corybooker-1209-ipadbackground_image_606w Newark Mayor CoryBooker (Lynne Sladky/Associated Press)

Newark Mayor Cory Booker (D) took a step closer to a Senate run this week, filing paperwork with the Federal Election Commission. 

Booker, who recently announced that he is exploring a 2014 bid, filed a Statement of Organization on Tuesday. Judith Zamore is listed as his campaign treasurer. 

To be clear, Booker has not officially said he is a candidate. But he's taking concrete steps in the direction of solidifying a bid. 

Meanwhile, Sen. Frank Lautenberg (D-N.J.) hasn't said whether he will run for reelection. Booker said in a Monday interview that Lautenberg has "a decision to make" about his future.

Fairleigh Dickinson University PublicMind survey released Thursday showed that that Democrats prefer Booker to Lautenberg by about a 2-1 margin.