Democratic voters in Wards 1-4 of Cambridge--the First Middlesex District--will choose two winners from a crowded fields of eight candidates for State Representative in tomorrow's primary election.

Since there will be no Republican opposition in November in the heavily Democratic district, the survivors of Tuesday's primary are guaranteed a place in the State Legislature.

The two incumbents are both seeking re-election. Rep. John J. Toomey is seeking his fifteenth consecutive two-year term, and Rep. Michael J. Lombard hopes to gain his fourth full term in the Massachusetts House.

But Toomey and Lombardi are looking over their shoulders at six determined challengers, all of whom say they have a shot at one of the two contested seats. City Councillor and former Mayor Alfred Vellucci--well known at this end of Mass Ave for his frequent outbursts against the growing presence of Harvard and MIT-in Cambridge--is probably the strongest of the pack, but the other five candidates must also be reckoned with:

* Michael J. Amato, unsuccessful candidate for City Council on the Cambridge Civic Association slate last year, has been running a well financed, highly visible campaign. Amato was the first Rent Control Committee chairman and has been active in several community action groups, including the Riverside Neighborhood Association and the Cambridge Community Center.

Amato says that in his campaigning he has stressed the lack of strong, credible leadership in the community. He is also quick to blame Harvard and MIT, with all their untaxable property, for the 40 per cent increase in property taxes over the last three years. He terms the current rent control law "unfair to tenants and landlords" and says that Cambridge, with six City Managers in six years, does not have a viable form of government.

* Doreen Blanc, a former high school teacher now working at Tufts, also complains of a lack of leadership, but the state level. Her chief interest is education and that is her main issue--racial inbalance in the schools, certification of teachers, how to pay for education.

Like most of the candidates, Blanc would replace the present flat-rate income tax with a graduate income tax, and reduce the property tax by finding other ways to finance the City's schools. And in another area, Blanc says. "There just have to be massive programs in housing. There must be state money for old and delapidated buildings, and we need a much stronger rent control law."

* John A. Minavich, a member of the Cambridge Economic Opportunities Committee, the Cambridge Committee for the Control of Housing and the local Model Cities program, is also in the race. Minavich classifies himself as the common man's candidate--a factory worker and a tenant: "I know the problems of making the first-of-the-month payment. I'm in with the average people and the average people are in with me."

That theme is heard again when Minavich talks about the issues: "I'm going after the tax rate in Cambridge," he says. "The only way to alleviate the tax proplem is to charge the universities....Anything that benefits the average working man is great. The average landlord is honest, but it's the out-of-towners who come in to speculate and cause trouble."

* Nicholas J. Mitropoulos, 20, is a senior at Boston University majoring in Political Science. He has worked for the City's Department of Public Works and has a large following among young people because of his work in recreation for the Model Cities program. "My basic push has been 'Give me a chance because what has the other guy been doing for you--it's time for a new face," says Mitropoulos.

Mitropoulos favors a graduated income tax and the use of the state's highway fund to improve the MBTA. He would not support a bill to tax university property because he thinks too many schools would be hurt tadiy by it. He would urge the state to take over the cost of County government, which cost Cambridge almost two and one-half million dollars last year.

* Lawrence R. Opert, a lawyer, is probably the weakest of the eight candidates. He admits that he would he "very surprised" if he won in the primary. Opert is relying heavily on 18,000 brochures he sent out over last weekend which listed his credentials for the job. He has been an assistant Professor of Finance at the Boston University School of Commerce and Business Administration, has "Icetured extensively throughout the United States on government spending, contract management, and cost effectiveness," and authored a master plan for policy training in Massachusetts.

Along with the standard view on reduction of taxes. Opert raises some issues which mark him as an attorney. He would campaign for such causes as a legislative review of the performance of Massachusetts judges, preferential treatment to the disadvantaged in the giving of state and municipal jobs, effective prisoner rehabilitation and penal reform programs, and the adoption of irreconcilable difference as an additional ground for divorce in Massachusetts.

VELLUCCI towers above the other challengers because of his long record in City politics: four years on the School Committee, 18 years on the City Council (eight as Vice Mayor) and two years as Mayor of Cambridge. It is Vellucci who has most strongly attacked Harvard for expanding deeper into Cambridge while failing to share the tax burden for services such as police, fire protection, water and transportation.