By Alexander Bolton - 06/29/10 03:51 PM EDT
The influential post became vacant with the death of Sen. Robert Byrd (D-W.Va.).
Lautenberg is the sixth-ranking member of the Homeland Security panel. Four Democrats who rank ahead of him already serve as appropriations subcommittee chairmen and cannot take over a second subpanel.
Lautenberg lost 18 years of seniority when he retired from the Senate in 2000. Democratic leaders convinced him to run for Senate again in 2002 when Republicans threatened to capture the seat held by Sen. Robert Torricelli (D-N.J.), who became embroiled in an ethics scandal.
Senate Appropriations Chairman Daniel Inouye (D-Hawaii) announced in a statement Tuesday that Lautenberg would take over as interim chairman.