Newton, N.J. — On one hand, there's Congresswoman Millicent Fenwick who is tall with patrician looks and a low, well-modulated, emphatic, and theatrical voice. She is known for her 14-hour workdays and her striking candor.
On the other, there's millionaire businessman Frank Lautenberg who is short and compact and has a pleasant face and snow-white hair. He's known for being warm and friendly.
Four-term Representative Fenwick has never lost an election. The Republican moderate is said to be the inspiration for the Lacey Davenport character in Gary Trudeau's ''Doonesbury'' comic strip. She keeps a work, campaign, and social schedule that might have exhausted Teddy Roosevelt.
Democratic candidate Lautenberg, chairman of the board of Automatic Data Processing (ADP) Inc., with 15,000 employees worldwide and 4,000 in the Garden State, is no stranger to hard work, either. But according to the polls, he's still a stranger to many voters. He expects to spend as much as $3 million on the general election, on top of the $1.9 million he spent to win the primary. Most of this money, he says, will be used to buy television time to tell voters he's running and where he stands on the issues.
Notwithstanding his success in the June Democratic primary, Mr. Lautenberg now finds himself largely where Jeffrey Bell, whom Mrs. Fenwick handily defeated in the GOP primary, was this spring. Mr. Bell spent $2 million. Yet the voter recognition and media attention he needed to defeat Mrs. Fenwick eluded him.
According to the most recent poll conducted by the Eagleton Institute of Politics, Mrs. Fenwick leads Lautenberg by 17 points.
Many observers wonder whether President Reagan, who campaigned for Mrs. Fenwick here in New Jersey Sept. 17, might well help her opponent more than the Congresswoman. In fact, some of her closest advisors reportedly warned that the President's active support may backfire by underscoring the effect Reaganomics is having on the economy. But the Fenwick campaign is banking that the President's tremendous personal appeal, coupled with some signs of an improving economy, will help more than hurt.
Former Vice-President Walter F. Mondale has campaigned for Lautenberg, and Sen. Edward M. Kennedy (D) of Massachusetts will in the next few weeks.
Lautenberg's father was a Patterson, N.Y., millworker, whose passing left his family penniless. ''I had on-the-job training in poverty,'' Lautenberg says. His family lived in the slums and some nights went to bed hungry, he adds. After serving in World War II, he went to college on the GI bill and joined ADP when it had just a few employees. (In its last fiscal year, ADP grossed $700 million.)
Mrs. Fenwick's father, however, was a wealthy Wall Street financier, who built a 50-room ''summer cottage'' for his family in Bernardsville, N.J. Mrs. Fenwick still lives in the small section of that home that remains. But later in life, divorced and deeply in debt, she, too, learned the meaning of hard work. Eventually, she served an editor of Vogue magazine for 14 years before entering public life in 1958 as a member of the Bernardsville Borough Council.
Mrs. Fenwick was elected to the New Jersey State Assembly in 1969, and appointed state director of consumer affairs two years later. She was first elected to Congress in 1974.
Although Lautenberg has spent his professional life in business, he's also had public service jobs. He's been on the boards of numerous volunteer organizations and serves as a commissioner of the Port Authority of New York and New Jersey, a bistate agency.
Lautenberg's campaign will undoubtedly help voters learn more about what he stands for. But his anticipated spending - with a sizable chunk expected to come out of his own pocket - might also hurt him, some analysts contend.
''It's the kind of thing that could well backfire on him,'' says Phillip Birch of the Bureau of Government Research at Rutgers University. Voters are more alert today to charges that candidates try to ''buy elections,'' he explains.
Mrs. Fenwick herself doesn't make that charge - at least directly. But it comes up at almost every campaign stop.
''Do you have to be millionaire to run for office?'' she asked recently in Newton, N.J., a Republican stronghold. ''No. . . . You can . . . work your way up, learning every step of the way. . . . I'm independent. Nobody pressures me! And nobody has the right to . . . say, 'We supported you, didn't we? You'd better vote for this.' ''
The Fenwick campaign has cost $780,000 so far, compared with $1.8 million spent by the Lautenberg camp.