(CNN) - A spirited Sen. Frank Lautenberg formally announced Friday he would not seek re-election in 2014, a decision his office made public the day prior.
As he stepped into the event in his hometown of Paterson, New Jersey, the longtime senator was greeted by thunderous applause from supporters, campaign staff and friends.
"Is it too late to change my mind?" Lautenberg joked as he approached the podium to speak.
After weeks of speculation of whether he would seek another term, Lautenberg's decision against running will spare the state (and himself) a primary challenge from Newark Mayor Cory Booker, a Democrat who's announced intentions to run in 2014.
The senator made no mention of Booker, though he's taken a few swipes at the young mayor in recent weeks. Polls, however, have indicated Booker would be the sure favorite in a match-up against Lautenberg.
While he's leaving office in two years, Lautenberg pledged to keep working during that time (and beyond) for issues such as climate change, gun control, education and transportation.
"I'm not announcing a retirement. I'm announcing today that I will be continuing on my mission to do the right thing wherever I can," he said.
Lautenberg, 89, returned to the Senate in mid-January after missing key votes over a weeks-long absence due to a cold which "turned into the flu, turned into a severe case of bronchitis with fluid in the chest," he said last month.
In a statement released by the White House, President Barack Obama called Lautenberg "a steadfast champion of the people of New Jersey."
"Throughout his time in the Senate, Frank has fought tirelessly for workers, veterans, members of our military and their families, and immigrants, and he continues to make extraordinary contributions to our nation's safety, and the health and welfare of our citizens," he said. "His service in World War II is a testament to his character and deep commitment to public service. I look forward to working with Frank on critical issues before us these next two years, and Michelle and I wish him and Bonnie all the best."
When Booker formed a Senate campaign committee last month to explore a run for the seat, a Quinnipiac University poll released around the same time found Booker would lead Lautenberg 51% to 30% in a head-to-head matchup. A new poll from Monmouth University indicated Booker with a 15 point advantage.
Booker's moves led to testy language between the two men and their staffs, though Booker also expressed his "love" for Lautenberg. Lautenberg said at the time he had no plans to retire.
Democratic Rep. Frank Pallone told CNN after Thursday's announcement, "I will say his not running [Lautenberg] changes the political landscape and I've always been interested in the Senate, and I'm going to continue to explore running."
He declined to comment on a potential primary match-up between he and Booker, saying "this is Senator Lautenberg's day." Pallone stressed that he and Lautenberg had a history of working together on several issues, including environmental programs, coastline protection and toxic waste cleanup.
The same Monmouth poll also indicated that if Lautenberg decided against running for re-election, 38% of Democrats said they should rally around with Booker, with 31% saying other candidates should get into the primary race.
Lautenberg becomes the fourth senator this year to announce that they won't run for re-election in 2014. Fellow Democratic senators Jay Rockefeller of West Virginia and Tom Harkin of Iowa last month announced they would retire from the Senate instead of making bids for re-election next year, as did Republican Saxby Chambliss of Georgia.
Other senators considered potential 2014 retirees are Democrats Carl Levin of Michigan and Tim Johnson of South Dakota, as well as Republicans Thad Cochran of Mississippi and Mike Enzi of Wyoming.
Lautenberg's seat is one of 21 around the country which Democrats are defending next year. They currently hold 53 votes in the chamber and two independent Senators regularly vote with the Democrats.
Sen. Michael Bennet, D-Colorado and chairman of the Democratic Senatorial Campaign Committee, wrote in a statement that he appreciated that "Lautenberg has made an early decision, giving us the time we need to get behind a strong Democratic candidate. We're confident that next November we will elect a new Democratic senator who will carry on Frank Lautenberg's proud tradition of fighting for New Jersey."
"I've been privileged to see firsthand Frank Lautenberg's incredible commitment to the people of New Jersey and the health and well being of all Americans," Bennet wrote. "He is a tireless and dedicated legislator and he will be greatly missed by his colleagues and constituents."
Lautenberg was first elected to the Senate in 1982 and was re-elected twice. He did not seek re-election in 2000 when his third term expired, but was recruited to run again two years later after Democratic Sen. Robert Torricelli quit his re-election bid weeks before the polls opened among charges of ethical issues. Lautenberg won that race in 2002 and was then re-elected in 2008.
"In case you weren't aware, I'm not standing for re-election in 2014. But I'm praying that something goes wrong–and I have to be," Lautenberg said Friday in a veiled joke about the situation that got him back in the Senate 10 years ago.
Lautenberg is the last remaining veteran of World War II to serve in the Senate and was a member of the United States Army Signal Corps from 1942-1946, according to his biography. In his retirement speech Friday, he credited the GI Bill for his education at Columbia University in New York.
He currently serves on the powerful appropriations committee, as well as on the environment and commerce committees in the Senate.
Chris Christie, New Jersey's Republican governor, praised Lautenberg in a statement Thursday that also pointed out where they disagreed.
"Frank Lautenberg and I have had our differences through the years, but I've always respected him for his tenacity, devotion to the people of New Jersey and his love for and commitment to public service. I will always be grateful for his doggedness in fighting with me and the delegation to ensure congressional passage of an aid package after Hurricane Sandy that is delivering necessary assistance to our residents," said Christie.
In his remarks, Lautenberg left a parting message to the young people in the room.
"This is a country where dreams are possible. You're looking at it," he said. "We see it all the time, and we have to continue to provide that incentive."
- CNN's Dana Bash, Kevin Bohn, Gregory Wallace, Paul Steinhauser, Ashley Killough and Adam Levy contributed to this report.