Christie has scheduled a special election for October to fill the seat until it expires in January 2015. The winner of that election would have to run again in 2014.
Lautenberg served nearly 30 years in the Senate. The liberal Democrat was 89.
Rep. Rush Holt became the first Democrat on Thursday to announce he's seeking his party's nomination for the seat. Former Bogota Mayor Steve Lonegan is to announce Thursday that he'll seek the Republican nomination.