"For a variety of reasons, personal and professional, all of them positive and optimistic, the end of this year seems to me to be the right time to step aside and ask the voters to select the next representative."
Holt's announcement surprised Democrats and immediately set off a scramble among veteran legislators for his seat.
First elected to the House in 1998, Holt has carried the 12th District with ease over the years, frequently winning with greater than 60 percent of the vote. Redistricting has made the Central New Jersey seat safely Democratic.
"It's not every day that a teacher and a scientist also proves himself to be an electoral juggernaut," John Currie, the state's Democratic Party chairman, said in a statement.
Holt is a former assistant director of the Princeton Plasma Physics Laboratory, the largest research facility at Princeton University; his campaign bumper stickers proclaim, "My congressman IS a rocket scientist."
He won Jeopardy! five times in the 1970s and later beat the IBM supercomputer Watson.
Holt has helped secure $22 billion in federal funding for science and technology research and worked to control college costs.
He also has been a champion of environmental causes, including pushing to address climate change.
"Rush Holt's retirement from Congress is a huge loss for the environment. His scientific background and his dogged advocacy to fight climate change were unique," Doug O'Malley, director of the advocacy group Environment New Jersey, said in a statement.
"Rush was indisputably one of the foremost leaders of land and water conservation in the Congress," he said.
In a statement, President Obama said Holt's "legacy will live on in our labs, our universities, and our classrooms, where countless math and science teachers have been able to afford college thanks in part to the TEACH grants he helped create."
House Minority Leader Nancy Pelosi (D., Calif.) praised Holt for his "leadership in expanding stem-cell research, increasing funding for the National Science Foundation, and strengthening our infrastructure in sustainable development, renewable energy, and environmental health."
Holt has been a fierce opponent of the National Security Agency's surveillance dragnet, which he says renders Americans "suspects first and citizens second."
Earlier in his career, Holt waged a campaign for paper ballot backups to electronic voting machines.
Last year, Holt ran unsuccessfully in a special U.S. Senate election to fill the seat vacated by the late Sen. Frank R. Lautenberg. During the campaign, he suggested that the eventual winner, former Newark Mayor Cory Booker, was too inexperienced and not sufficiently liberal for New Jersey.
"Other candidates are talking 'progressive' this and 'progressive' that," he told The Inquirer over the summer. "I guess, maybe if I said 'liberal' instead of 'progressive,' they'd stop copying me on that. People are afraid to say 'liberal.' I'm not."
In his e-mail to supporters Tuesday, Holt declined to say what he might do next.
Republican Alieta Eck, a Somerset County doctor who also lost in the special-election primary last year, announced her candidacy for Holt's seat last month.
"I was looking forward to debating the critical issues facing America and New Jersey with Congressman Holt," Eck said in a statement Tuesday. "But my campaign was [not] and will not be about my opponent," added Eck, who is running on her opposition to the Affordable Care Act.
Democrats who immediately expressed interest include State Sen. Linda Greenstein and Assemblymen Upendra Chivukula and Reed Gusciora.
A spokesman for Chivukula, who ran unsuccessfully against Republican U.S. Rep. Leonard Lance in a different district last cycle, said the assemblyman would make an announcement Wednesday.
"I thought Rush Holt had a long shelf life," Gusciora said in an interview. "It's all taken us by surprise. He's been a great congressman."
He added: "The interesting thing about Central Jersey: We have no power brokers. The decision truly won't be made in the back room."