A member of Newark Mayor Cory Booker’s campaign staff says Booker is planning to enter the special election to fill the U.S. Senate seat previously held by Frank Lautenberg.

The staff member says Booker plans to announce his entry into the race Saturday. He spoke on condition of anonymity because he was not authorized to speak publicly on the plans ahead of the official announcement.

Booker had been expected to run. He announced last year that he was considering seeking the office in 2014, and he has been raising money for a run.

Lautenberg died Monday at 89.

A special primary is scheduled for August with a general election in October.

(AP)