Frank Lautenberg (Chip Somodevilla/Getty Images)
Sen. Frank Lautenberg of New Jersey has decided not to run for re-election next year, sparking what could be a contentious battle among Democrats for the open seat.
"This is not the end of anything," Lautenberg said Thursday in a statement. "While I may not be seeking re-election, there is plenty of work to do before the end of this term and I'm going to keep fighting as hard as ever for the people of New Jersey in the U.S. Senate."
Lautenberg, 89, is the Senate's oldest member and has been pushing new gun-control measures. He will make a formal announcement Friday in his hometown of Paterson.
Newark Mayor Cory Booker has already declared his intention to run for the Senate next year, causing some awkwardness in the heavily Democratic state. Rep. Frank Pallone, a longtime congressman, has wanted to run for the Senate if Lautenberg retired.
Lautenberg suggested Booker deserved a "spanking" for openly coveting his Senate seat, and said he was sure the mayor would not be a "lone soldier" in a 2014 race. Polls by Quinnipiac, Fairleigh Dickinson and Monmouth universities show Booker would have had a substantial lead over Lautenberg in a Democratic primary.
Ruth Mandel, director of the Eagleton Institute of Politics at Rutgers University, said Lautenberg's decision is not much of a surprise given his age.
"He's probably decided that a six-year term and a tough campaign is not the right thing for him at this stage of life," Mandel said. "He loves that position and very much regretted stepping down the last time. ... It's a realistic look at what one can do at a certain point."
Lautenberg is on his second stint in the Senate: He represented New Jersey from 1982 to 2001, retired for a short time, then successfully ran again in 2002. He is best known for writing legislation that established a minimum blood-alcohol standard of .08 for drunken driving and for authoring the law banning smoking on airplanes.
Lautenberg is also the last World War II veteran serving the U.S. Senate. Two members of the "Greatest Generation" - Democrat John Dingell of Michigan and Republican Ralph Hall of Texas - serve in the U.S. House.
In his statement, Lautenberg vowed that he will spend the rest of his term on gun-safety measures, legislation to protect children from toxic chemicals and efforts to create more jobs in New Jersey.
Even with Lautenberg's retirement, the Senate seat is likely to remain in Democratic hands. Voters in New Jersey gave President Obama a nearly 18-point victory in November.
On the Republican side, TV and radio reporter Geraldo Rivera has said he is contemplating a race.