Seeking to rally left-wing forces before the upcoming presidential election, one-time radical activist Tom Hayden and his wife, actress Jane Fonda, are launching a month-long, 50-city national speaking tour next week.

Starting with an appearance in New York Sunday on NBC'S "Meet the Press," Hayden and Fonda will be visiting such key primary states as New Hampshire, Massachusetts, Illinois, Iowa and Michigan during their eastern swing. They will speak ot labor, consumer, campus and community groups sympathetic to the goals of their California-based Campaign for Economic Democracy.

CED, which claims over 4,000 members in some 25 chapters scattered across California, has a yearly budget of $250,000 supported largely by donations from Fonda, local fund raisers and membership dues. The tour, estimated to cost more than $100,000, will be financed entirely by honoraria paid to Hayden and Fonda by college and community forums.

The tour's itinerary, as well as its timing, has led many in state and national politics to wonder if the trip amounts to more than an advance party for the presidential campaign of California Gov. Edmund G. Brown Jr., a close political ally of Hayden, Fonda and others involved with CED.

"They aren't fooling anyone around here," said California state assemblyman Richard Robinson, a leading Democratic critic of both CED and Brown's appointments of Hayden and Fonda to various state offices. "Their whole trip is a little preliminary Jerry-Brown-for-president-tour."

While admitting he's "leaning" toward an eventual endorsement of Brown's candidacy, Hayden insists he and Fonda are making the tour to build up a "progressive citizen's movement" that would serve to pressure White House hopefuls on issues like nuclear power and solar energy. Hayden and other CED organizers repeatedly have reassured anxious tour sponsors across the country they will not front for Brown.

"We told them we would only sponsor the tour if they said they would not be stalking horses for Brown. We just want them to talk about economic democracy," said Jeff Brumner, coordinator of the Granite State Alliance, a New Hampshire citizen action group sponsoring Hayden-Fonda appearances in that primary state.

Brumner and other tour sponsors said that any attempt to promote the Brown candidacy in New England could only backfire on Hayden, since most local Democratic activists already prefer Sen. Edward M. Kennedy for the 1980 presidential nomination.

"The Brown connection is something we are skeptical about," Brumner said. "His cosmic consciousness thing won't work here. New Hampshire is different from California. That Brown stuff just won't wash well with Yankees."

Hayden asserts that the choice of a candidate to back next year is of less importance to the American left than the need to organize around the issue of economic democracy. Allied to this stance are CED's opposition to nuclear power, its encouragement of a decentralized solar energy industry, and a call for citizen and worker representation on the boards of major American corporations.

"The tour addresses issues that go far beyond tomorrow's concern. The Kennedy and Brown thing is not all that important," Hayden said. "The big issues are corporate power and energy. They are bigger than the office of the president. The important thing is developing a groundswell of citizen opinion beneath the candidates in order to make them accountable."

The tour marks a major turning point for Hayden's political career.In the early 1960s he was one of the founders, and perhaps the leading ideologist, of a the militant Students for a Democratic Society. In recent years, he has worked to fashion CED into a vehicle to further his ambition for elective office.

Hayden surprised many California politicians in 1976 by polling more than 1.2 million votes in his unsuccessful primary race against former Democratic senator John Tunney. Aides say that Hayden is preparing for another Senate bid in 1982, this time for the seat occupied by Republican S. I. Hayakawa, the man who defeated Tunney in the 1976 general election.

The 50-state tour is expected to help Hayden reestablish his credentials as a national leader of the left and enable him to link up again with friends from his SDS days who are emerging as leaders of citizen action groups in various parts of the nation.

Ira Arlook, executive director of the Ohio Public Interest Campaign, believes the current push for economic democracy is an offspring of the early SDS and its "Port Huron Statement," drafted by Hayden and other activists at a 1962 SDS convention in the Michigan resort city. The statement called for broad participation in the political process and a society freed from what its drafters viewed as pervasive control by governmental and corporate bureaucracies.

Arlook, once an SDS activist, envisions a coalition of groups such as CED and his Ohio organization as a unifying force behind a new, broadly based left-wing populist movement.

"We all come out of one tradition," he explained. "We still work together and find ourselves together on this tour. The key to it is that democracy means something and it should be lived up to. If you read the Port Huron statement, that's what it's all about."

The reemergence of the SDS leadership is largely the product of a 1975 meeting, held outside Los Angeles, at which former members of the group agreed to work for the expansion of rent controls, lower utility rates, and otherwise do what they could to broaden their appeal to mainstream America.

With the country moving into a recession, these former radical leaders view the 1980s as a time of opportunity to effect social and economic change.

"This is a much broader base than we had in the 1960s," said Mike Ansara, staff director of Massachusetts Fair Share, a statewide citizens' action group, and another SDS veteran."All over the country people are getting organized on economic issues. It'll be interesting to see if Hayden can become the popularizer of these issues."

The key to such an effort, Hayden and other former New Left leaders believe, will be their ability to build bridges to the labor movement.

Hayden's success in scheduling an appearance before next month's convention of the United Auto Workers in Des Moines suggests the outreach effort is bearing fruit. Chuck Gifford, president of the UAW's Iowa Council, said there was still "some suspicion" of Hayden from the SDS days, but that most of his members were receptive to listening to the Hayden-Fonda message.

"If they subscribe to economic democracy, then they're okay," Gifford said. "I really haven't gotten too much criticism on this. After all, everyone is interested in seeing Jane Fonda and most don't remember who the hell Tom Hayden was back then, anyway."