While I agree with the conclusions of the Nov. 11 editorial on the Arias plan for Central America, I must attempt to correct the premises on which its conclusions were based -- namely, that the contras have a broad base of support in Nicaragua and that the Nicaraguan government stifles dissent and disenfranchises the middle class.

I recently returned from five weeks living with a campesino family in Esteli, about 150 miles north of Managua. During that time I attended seminars -- sometimes twice a day -- on all aspects of the society and government. I also met with opposition party members; U.S. citizens living and working in Esteli, Matagalpa and Managua; middle-class Nicaraguans; religious leaders; government representatives; Sandinista party members; and the director of the Commission on Atlantic Coast Autonomy, who is a Miskito Indian. Further, I observed the open border with Honduras on Oct. 3 and interviewed two people who accepted the amnesty for expatriates and contras who wish to return to a normal life in Nicaragua. Both the open border and the amnesty program are unilateral responses on the part of the government to demonstrate its desire for the Arias plan to work.

It is important for Americans to realize that there is a middle class in Nicaragua, that the revolution is a concept independent of the FSLN (the Sandinista party) and that the FSLN is a party independent of the government. Many middle-class Nicaraguans, especially those living in Matagalpa and Managua, oppose both the revolution and the Sandinistas. That is not surprising. The middle class as a whole is much worse off now than it was under Anastasio Somoza. Inflation is at about 1,500 percent, rendering money practically worthless. One must allow 10 minutes at the end of a restaurant meal to count cordobas because a party of four can easily have a bill approaching 100,000 cordobas or more, and denominations of larger than 1,000 are scarce. Nevertheless, there are many middle-class people who support the revolution, who do not wish to return to conditions like those under Mr. Somoza, but who disagree with how the government and the majority FSLN party are managing the country. These people have several other parties to choose from, which are represented in the National Assembly. What is surprising is that there are many middle-class Nicaraguans -- especially in Esteli -- who not only welcome the revolution but support the efforts of the Sandinista party to create a pluralistic society and a mixed economy.

It is also important for Americans to realize that the 1984 elections were free and fair. The fact that the party that now constitutes the contra leadership boycotted the election is usually left out of descriptions of those elections. We will never know if the Sandinistas would have been defeated by members of that opposition, because people who would have voted for them couldn't -- they weren't on the ballot by their own choice. The outcome of the election is a matter of public record: close to 65 percent of the people who voted (about 75 percent of registered voters) elected the Sandinistas. No one should be surprised that the FSLN won the election. The Sandinistas threw out Mr. Somoza and some of the worst oppressors and torturers in recent history.

To date, the contras have not succeeded in establishing an alternative government in any territory. There are definitely regions where they have more freedom of movement, and they undoubtedly have a following and an appeal in certain areas. But the campesinos I lived with and talked with are sure that if the contras and the parties that support them took over, the common people would lose.

As our own experience during the Reagan years has shown, those who cannot afford to buy basic needs must rely on the charity of a society that is all too often reluctant to share its abundance. In Nicaragua, the peasants have been given education, medical care, food, land and the means to defend them. The strength of the working class and the poor is not in their money, but in their commitment to the process that will ensure that their voices are heard. Overthrowing that kind of a revolution will be difficult indeed. As The Post's editorial concludes, the negotiating table is where the focus must be. JO UNCAPHER Washington