Andrews, 50, said he's met 40,000 people since announcing his challenge to Lautenberg in April and contrasted his campaign schedule with the 84-year-old Lautenberg.
"I've answered thousands of questions," Andrews said.
But he said many people ask him, "Where is the senator?"
"We have someone who's been in Washington for nearly 30 years who seems to think he's entitled to this seat rather than the fact that he has to earn it," Andrews said.
The primary is June 3.
"The absentee is Rob Andrews, who has missed over 70 percent of recent votes in Congress," Lautenberg spokeswoman Julie Roginsky said. "And it's Rob Andrews who has chosen to wage a campaign of false personal attacks against Sen. Lautenberg while running away from his own record of co-writing Bush's resolution to get us into the Iraq war and siding with Republicans on tax breaks for the wealthiest 1 percent of Americans."
Andrews' campaign is running a television ad that focuses on the age issue, calling Lautenberg's successful Senate campaign against Rep. Millicent Fenwick in 1982 "one of the low points in New Jersey political history."
Fenwick was 72 at the time, and Lautenberg questioned her fitness for a Senate seat.
The Andrews ad concludes, "It's hard when your own words come back to haunt you, isn't it, Mr. Lautenberg?"
Andrews had said he wouldn't focus on Lautenberg's age, but on Tuesday said, "What changed is the senator became an absentee candidate."
Roginsky cited Lautenberg's legislative efforts to combat increasing gas prices as an example of his activism.
"Andrews talks," she said. "Lautenberg gets the job done for New Jersey."
Andrews, though, challenged Lautenberg to reveal how much money he earns from energy company stocks as gas prices rise.
"How much is he earning off of this problem New Jerseyans are experiencing?" Andrews asked.
Roginsky said Lautenberg's financial disclosure reports show "almost no interest on his part in oil stocks."
