The abortion issue hardly came up in Richard Kraus' campaign for the Massachusetts Senate. Like most candidates this fall, Kraus talked mainly about the economy.

However, the victory of this soft-spoken Harvard Ph.D in the Democratic primary was evidence of a quiet guerrilla war waged by a newly sophisticated "pro-choice" movement. Stunned by the 1978 and 1980 election victories of right-to-life activists, the once complacent defenders of legalized abortion began building political machines across the country whose impact will be felt for the first time this year.

Kraus, 45, won his primary after getting $9,000 -- a fourth of his budget -- from the political action committees of the National Abortion Rights Action League (NARAL) and the Massachusetts Organization for the Repeal of Abortion Laws (MORAL). Two of his four paid staffers were abortion rights activists and some 200 MORAL-trained volunteers pitched in.

It took a lot of "soul searching" before he accepted the help, said Kraus, who is unopposed in the general election. "But I don't believe we could have raised that money any other way -- which means I would have lost."

Evidence is mounting that support for legalized abortion is not the political liability it was in 1980. Out of 150 state and federal candidates targeted for help by NARAL and its local affiliates, 120 won tight primary races.

"The politics of abortion have changed dramatically since 1980," says Nanette Falkenberg, a political organizer for the American Federation of State, County and Municipal Employes who was hired as NARAL's executive director. "This year candidates are learning that being pro-choice is good politics. It brings support, campaign assistance and votes."

The group is focusing on state legislatures, which will be faced with the abortion issue if a constitutional amendment comes out of Congress. But NARAL's political action committee has also spent $500,000 on a dozen U.S. Senate campaigns and 102 U.S. House races. Another group, Friends of Family Planning, spent more than $300,000.

To be sure, the pro-life movement is still alive and well. Mid-October Federal Election Commission reports show campaign expenditures for the national Right to Life Political Action Committee at $240,000; for the national Pro Life PAC at more than $300,000; for the Life Amendment PAC at more than $320,000.

But infighting among anti-abortion groups over legislative strategy and the Senate's refusal this fall to take action on an anti-abortion bill sponsored by Sen. Jesse Helms (R-N.C.) have slowed the momentum of pro-life organizations.

Now, with the new political activism of pro-choice groups -- NARAL's membership jumped from 80,000 to 150,000 in two years -- the balance of power is changing and the outcome is far from certain.

Massachusetts, a heavily Roman Catholic state with a long history of controversy over abortion, is a good place to look at grass-roots activity on the issue.

The Massachusetts Citizens For Life (MCFL), an anti-abortion group that has 45 chapters, 7,000 members, a staff of four and $100,000 budget, celebrates its 10th anniversary this year.

MORAL is also 10 years old. In the last four years, its membership grew from 200 to 4,000, its paid staff from one to nine and its budget from $3,000 a year to $178,000.

Kraus is one of seven state senate candidates targeted for help by MORAL this year. Five won their primaries, which is tantamount to election here. That could tip the balance of power in the state senate where abortion rights activists have been two or three votes short of the one-third necessary to stop a constitutional amendment outlawing abortion.

State Sen. George Bachrach beat three challengers after receiving $8,000 from MORAL and NARAL political committees.

"One of the things liberals do badly is put their money where their mouth is," he says. "But MORAL provided real flesh and blood people who held signs on rainy days and handed out leaflets on hot days."

Pamela Lowry, a founder of MORAL, said that when anti-abortion groups organized to overturn the Supreme Court's 1973 decision legalizing abortion "we had no clear vision of what to do. For us, politics were still a little dirty. We were still with the white gloves."

But in 1978, MORAL hired Jean Weinberg, a community organizer of the Saul Alinsky school, who came up with a plan, later adopted nationally, to organize from the bottom up. Now, each weekend, MORAL cardtables can be found in Harvard Square and suburban shopping centers. Passersby sign "I am pro-choice and I vote" postcards.

Signers are invited to meetings in private homes in their neighborhoods. There they are given a talk, view a slide show and are invited to sign up for phone banks and fund raising. They attend political skills workshops and are able to move into targeted campaigns.

Lowry now runs computers for Michael Dukakis, recently nominated for a second term as governor after defeating Gov. Edward J. King, a pro-life candidate. A former MORAL staffer is working as a paid fund raiser for Democratic Rep. Barney Frank in a tight race against Republican Rep. Margaret M. Heckler.

Today many of MORAL's members are attracted to the group more for its reputation as a training ground for political organizing than for its advocacy of the abortion issue.

"I barely remember when abortion was illegal," said Nancy Levin, 26, who succeeded Weinberg as head of MORAL and now coordinates seven states. "I became involved in abortion rights more for what I could learn about political power."

While MORAL concentrates on organizing people who are already pro-choice, the anti-abortion MCFL focuses on trying to convince people that abortion is murder.

James Lyons Jr., an anti-abortion candidate who ran against Kraus, said he was surprised going door to door that more single-issue voters were pro-choice than pro-life, a development that national polls have confirmed.

Usually on the Sunday before an election in Massachusetts leaflets are distributed in the parking lots of Catholic churches by pro-life groups, a tactic that might yet prove effective this year. But so far, there is little evidence of direct involvement by the church, possibly because a pro-life letter from the archbishop in 1980 drew a backlash, and ended up helping Barney Frank, one of the candidates it was ostensibly directed against.

With a full-time lobbyist at the statehouse, MCFL has been successful in passing legislation, much of which has been challenged in court. It has distributed 60,000 newsletters endorsing state and federal candidates, and has contributed $8,000 to congressional candidates.

Most of its political activity is left to local chapters of erratic effectiveness, however. "We've got our phone banks going," said MCFL President Marianne Rea-Luthin. But she said of MORAL: "We don't have the money they do. They're well-organized."