(CNN) - Mayor Cory Booker of Newark, New Jersey, has created an official campaign committee, marking a significant first step towards a 2014 Senate bid, Federal Election Commission documents show.
The non-descript but important paperwork registering "Cory Booker for Senate" was filed on Tuesday. It was first reported Friday by the Star-Ledger newspaper of Newark.
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Booker, a Democrat, said in December he would run for the seat currently held by Sen. Frank Lautenberg, who is also a Democrat. Lautenberg is currently the oldest member of the Senate and is days away from turning 89.
A recent poll showed 42% of Democrats and those leaning Democratic would support Booker and 20% would favor Lautenberg.
Booker chose not to run in the 2013 race for governor against Republican Gov. Chris Christie, who has enjoyed especially high approval ratings since his handling of Superstorm Sandy. He made the decision, he said, in order to serve out his second term as mayor.
Lautenberg's spokesman, Caley Gray, said a report that "Senator Lautenberg has decided to retire is simply not true."
Politico separately reported that a Lautenberg aide who would not speak for attribution called the decision to challenge an incumbent Democrat rather than an incumbent Republican "shameful."
The FEC form says little of his Booker's bid but is an important step in running for federal office. The particular form Booker must be submitted within 10 days of accepting contributions over $1,000 or creating a campaign committee.
- CNN's Gregory Wallace and Kevin Bohn contributed to this report