NEWARK, N.J. - A Democratic congressman is making age one of the central themes in his fight to unseat Sen. Frank Lautenberg, reminding voters that if re-elected, the New Jersey senator would be nearly 91 by the end of his next term.

In one television ad, Rep. Rob Andrews reached back to Lautenberg's 1982 Senate campaign, when Lautenberg himself questioned an opponent's age.

Andrews' bid was one of the top races on the ballot in today's primaries, when voters in seven states decide a host of congressional contests and ballot initiatives.

In New Jersey, Andrews disregarded the wishes of party leaders, who urged him not to challenge Lautenberg to avoid a costly, divisive primary.

Andrews, 50, who has served in the House since 1990, recalled in the ad how Lautenberg raised the age issue when campaigning against Rep. Millicent Fenwick, who was 72. "It's hard when your own words come back to haunt you, isn't it?" the ad asks.

Lautenberg, 84, insisted he was criticizing Fenwick's age relative to her political experience. He is the third-oldest senator on Capitol Hill. Democrat Robert Byrd of West Virginia is 90, and Republican Ted Stevens of Alaska is two months older than Lautenberg.

In a debate last week, Andrews denied that Lautenberg's years were the issue.

"I think that he's not effective in the U.S. Senate," Andrews said. "I think it's his level of commitment for the next six years."

Lautenberg said Andrews "has done everything he can to assault my age. He doesn't talk about my effectiveness. He doesn't know effectiveness when he sees it. He hasn't had any of it" in Congress.

Lautenberg amassed $4.3 million for the campaign and lined up support from many of the state's most influential Democrats, including Gov. Jon S. Corzine.

Andrews, who had to relinquish his House seat to run for Senate, had $2.4 million for the race in early April.

Lautenberg and Andrews have largely ignored a third Democrat seeking the nomination, Morristown Mayor Donald Cresitello. *