The Republican seat-warmer for New Jersey, Jeff Chiesa, was sworn into the Senate on Monday by Vice President Joseph R. Biden Jr.

New Jersey Republican Gov. Chris Christie appointed Chiesa to hold the seat until October, when a special election will be held to fill the vacancy left by the late Sen. Frank R. Lautenberg, D-N.J., who died last week at the age of 89. Chiesa was nominated by Christie in 2011 to be New Jersey’s attorney general, an appointed position in the Garden State, and served in that post from 2012 until his selection for the Senate seat last week.

Four Democrats already have announced their intent to run in the special election, with new polling indicating that Newark Mayor Cory Booker leads the pack. Lautenberg’s former seat is up in 2014, so whoever wins will have to immediately run again for re-election.

Chiesa was an assistant U.S. attorney from 2002 to 2009 and later served as Christie’s chief counsel.

The newly minted senator is a graduate of the University of Notre Dame and holds a J.D. from Catholic University. He has a wife, Jenny, and two children.

See Roll Call’s Senate Seniority List.