Rep. Rush Holt (D-N.J.) will run in the special election for a vacant Senate seat, caused by the death of Sen. Frank Lautenberg (D-N.J.), he announced Thursday.

"On Tuesday, Governor Christie announced a special election to fill the vacancy in the U.S. Senate," Holt writes on his campaign Web site. "Today, I ask for your support as I seek to serve as your Senator in that seat. The reason is simple: I believe I am the best candidate to continue the passionate advocacy for progressive values that Sen. Lautenberg exemplified."

Holt's entrance into the race adds another variable to a Democratic field that is expected to include Newark Mayor Cory Booker and Rep. Frank Pallone. While both of them come from North Jersey, Holt comes from the central part of the state, mostly Mercer and Middlesex counties.

Potential candidates don't have much time to decide whether to run. Petition signatures are due with the state by Monday. In his note, Holt asked supporters to help him collect signatures. Booker has also started collecting signatures.

Holt has represented his district since 1999. He is a research physicist by trade and once won five episodes of the popular game show "Jeopardy!"

It remains to be seen whether a candidate from South Jersey will enter the race. Generally, Democratic primaries in New Jersey are highly regional, and South Jersey remains the one region without a candidate.

The Republican primary for the seat has yet to take shape, and Gov. Chris Christie (R) has yet to name an interim appointee.

The primary is set for August, with the winner to be determined Oct. 16.

Updated at 10:24 a.m. on 6/6 with Holt's official announcement. Sean Sullivan contributed to this report.