Newark Mayor Cory Booker's (D) staff insisted there was nothing official about his potential 2014 Senate run, despite a filing with the Federal Election Commission to establish a campaign committee and raise funds for a run.

"Today, Mayor Booker filed papers to be prepared for a possible US Senate campaign, but his focus remains on completing his vision for a revitalized Newark - more than a billion dollars in economic development this year alone, reforming education for our kids, building housing and parks, and continuing to make progress in reducing crime and violence in the city," said Booker's political director Mark Matzen in an email to The Hill late Friday.

"As part of the process of exploring a possible senate run, the law requires any expenses in such an exploration to come from a federal account," Matzen added.

Booker's decision to file papers with the FEC, however, takes him that much closer to a run that most New Jersey Democrats see as more than merely speculative.  

The Newark mayor has indicated for some time he was considering seeking higher office, but his choice to pursue a seat currently held by Sen. Frank Lautenberg — who, though considered a top retirement risk for Democrats, has not yet announced his plan — has irritated some in New Jersey.

After announcing his decision to explore a potential Senate run late last month, Booker has received private backlash from Democrats active in New Jersey political circles who feel that, in choosing not to run for governor, Booker undermined the party's best chance at defeating Republican Gov. Chris Christie. 

Christie's high approval rating and the lingering memory of Hurricane Sandy, which most New Jerseyites polled say Christie handled well, could hand him another win in a state that voted overwhelmingly for President Obama in November.

Democrats have been unable to find a strong candidate to challenge the governor, and some believe Booker's choice to run for Senate was one made more out of self-promotion and less out of allegiance to the party.

However, recent polling indicates Booker might be a stronger bet for the Democratic nomination; he drew the support of 42 percent of Democrats, to 20 percent for Lautenberg, in one recent poll

On Friday, Lautenberg's staff pushed back on a report that he would be retiring in 2014.

"The news report that claims Senator Lautenberg has decided to retire is simply not true," said Lautenberg spokesman Caley Gray.