Rep. Millicent Fenwick, the feisty 72-year-old grandmother who gained fame as the real-life model for a comic strip heroine, yesterday won the New Jersey Republican senatorial nomination.

Fenwick was leading Jeffrey Bell, the 38-year-old conservative and former Ronald Reagan speechwriter, by 54 to 46 percent when Bell conceded three hours after the polls closed.

"It looks," he said, "like Millicent's magic was just too much."

On the Democratic side the winner was wealthy businessman Frank Lautenberg, who spent well over a million dollars in outdistancing two former House members, Andrew Maguire and Joseph LeFante. With 99 percent of the precincts in, Lautenberg had 26 percent, Maguire 23 percent and LeFante 19 percent.

Mercer County Freeholder Barbara Boggs Sigmund, daughter of Rep. Lindy Boggs (D-La.), finished fourth in the Democratic race with about 12 percent. Some angry Maguire backers said it was her late entry into the Senate race--a switch from a House contest--that split the liberal vote and beat Maguire. But Maguire pledged to back Lautenberg, who built a fortune as founder and head of Automatic Data Processing.

Turnouts were reported generally light as voters in 10 states, from Maine to California, chose candidates for four Senate seats, six governorships and more than 100 House races. Details on the Virginia voting, Page C1

In the hard-fought California Republican senatorial primary, San Diego Mayor Pete Wilson beat Reps. Paul N. (Pete) McCloskey Jr. and Barry M. Goldwater Jr. in their fight for the seat of the retiring Sen. S.I. Hayakawa.

Exit polls showed Attorney General George Deukmejian taking a suprising lead over Lt. Gov. Mike Curb in the GOP gubernatorial primary. Los Angeles Mayor Tom Bradley, as expected, was headed for the Democratic gubernatorial nomination and Gov. Edmund G. Brown Jr. took the Democratic senatorial nomination.

With 88 percent of the vote counted in the Ohio Democratic gubernatorial primary, Richard Celeste, the 1978 gubernatorial candidate, held a narrow lead over Attorney General William Brown, 42 percent to 37 percent, with former Cincinnati mayor Jerry Springer third with 21 percent.

In the GOP race Rep. Clarence J. Brown easily defeated former Cuyahoga County (Cleveland) commissioner Seth Taft, with a 3-to-1 lead.

In Cleveland, with 98 percent of the vote in, Rep. Ronald M. Mottl was narrowly trailing Cuyahoga County Commissioner Edward Feighan by only about 850 votes. Feighan is the nephew of former Ohio representative Michael Feighan and the candidate of Democrats angry with Mottl for his support of President Reagan's economic programs last year. Feighan had 47.9 percent of the vote to 47.59 percent for Mottl.

In Iowa, Roxanne Conlin won the Democratic gubernatorial primary. With only 26 percent of the vote counted her opponents, former lieutenant governor Jerry Fitzgerald and Democratic State Chairman Edward Campbell, conceded. Conlin had 43 percent, Fitzgerald 34 percent and Campbell 23 percent.

None of these races, however, offered a more intriguing matchup than that of Fenwick, the flesh-and-blood counterpart of the Doonesbury comic strip's Lacey Davenport, vying for the New Jersey Republican senatorial nomination against Bell, the former Reagan aide and conservative economic theorist who sought to make the race a referendum on Reaganomics.

They are seeking the Senate seat vacated by former senator Harrison A. Williams Jr. (D).

Outspending the wealthy four-term congresswoman, Bell charged in mass mailings and TV spots that she was Jimmy Carter's most loyal Republican supporter and too liberal to carry the Republican banner in November.

Fenwick replied that she backed Reagan's budget and tax cuts and stood with the president in defending the Federal Reserve Board's current monetary policies against criticisms from Bell, who made "reform" of the Fed one of the keynotes of his campaign.

At a more basic level, Fenwick argued that, with an unbroken record of wins in legislative and congressional races, she was a better bet in November than was her young opponent.

An NBC News analysis said Fenwick had run most strongly with liberal and moderate Republicans and among those who were best-educated. Despite her efforts to portray herself as a Reagan supporter, the network interviews indicated that she was strongest with those who were least approving of Reagan's policies.

Lautenberg, the network said, scored best with the elderly, Jewish voters and those from southern New Jersey.

Bell scored a major upset in his first bid for public office in 1978, when he surprised veteran liberal Sen. Clifford P. Case in the GOP primary. But in the general election that year he lost to former Princeton and New York Knicks basketball star Bill Bradley (D).

The seat for which Bell and Fenwick were battling was held until recently by Williams, who was convicted in the Abscam investigation last year and resigned rather than face a Senate expulsion vote. Republican Nicholas F. Brady is the interim, appointed senator.

New Jersey Democrats faced a list of nine candidates, with five regarded as serious contenders.

The leading spender was Lautenberg, a millionaire computer manufacturer and longtime Democratic fund-raiser, making his debut as a candidate at age 58.

Two former House members tried to best him with very different tactics. Ex-representative LeFante, 53, of Bayonne, relied on the muscle of the Hudson County Democratic organization, while Maguire, 42, put together a coalition of environmentalists, women's groups and some of the liberal unions.

But the Democrats had difficulty drawing public interest from the Fenwick-Bell battle in the other party, which seemed a classic clash of generations and philosophies.

In the last few years Fenwick has attained a degree of publicity unusual for a House member, both because of her outspoken criticism of congressional perquisites and practices and because television interviewers and feature writers found the pipe-smoking grandmother with a heart pacemaker a romantic, appealing figure.

Bell, who never stopped campaigning after the 1978 race, found himself 30 points behind Fenwick in the early 1982 polls, and admitted, "There's no way I can win a personality contest with Millicent."

But he kept hammering away at what he called her liberal voting record, criticized her stands on capital punishment, the Panama Canal, private school aid and school prayer, and tried, in his literature, to link her to such left-wing Democrats as ex-representative Bella Abzug of New York.

Fenwick insisted that she was a mainstream Republican, and painted herself as a better practical politician and problem-solver than is Bell.

"I don't care about these theories," she said of his detailed plans for overhauling Federal Reserve policies. "We've got to get people back to work."

In the most spirited House contest in New Jersey, Rep. James A. Courter (R), a conservative endorsed by Reagan, defeated Morris County Freeholder Rodney P. Frelinghuysen (R), son of ex-representative Peter H.B. Frelinghuysen (R) and scion of one of the state's leading political families.

Courter, who had been nudged out of his old district by a Democratic reapportionment plan, rolled up better than a 3-to-2 margin.