The Democratic National Committee has just completed its most exhaustive voter-attitude survey and come away with a stark conclusion: When Democrats make appeals based on "fairness," they are using a code word that now carries a negative connotation with most voters.

"Middle-class voters all over the country read 'fairness' as 'not me but some other guy,' " Frank O'Brien, director of the DNC direct-mail program, told the winter meeting of the Association of State Democratic Chairs here today.

"When party leaders talk about fairness, middle-class voters see it as a code word for giveaway," he added, noting that nearly 90 percent of those surveyed described themselves as middle class.

The finding comes from a national survey of 5,500 adults and from 43 focus-group sessions conducted this summer and fall by the DNC as part of a $200,000 research program to help determine what themes will work for the party in 1986.

The poll has not been fully tabulated, and the results were presented today in summary form, with few numbers attached.

Still, the report's implications raised a troubling question to many who heard it: Should the Democratic Party bow to the prevailing wind and abandon its historic commitment to the disadvantaged?

"It may help us elect more people, but it is not my mission as a Democrat," Arthur Davis, chairman of the Iowa Democratic party, told fellow state party chiefs.

His response was seconded by DNC Chairman Paul G. Kirk Jr., who said he would never head a party whose programs "leaves some disadvantaged behind."

The report makes clear, however, that voters are not of like mind.

"People are telling us, 'Please don't ask us to care for people down the street before we take care of our own family's economic security,' " said George Burger, DNC political director.

One direction suggested by the poll, he said, is a domestic platform structured around a set of "family economic-security" programs for the middle class. The poll found that 77 percent of Americans support low-interest loans for first-time home buyers and that 68 percent support college-education loans not based on a family's means.

A cautious note was struck by Lt. Gov. Richard J. Davis of Virginia: "When we begin to talk about these kind of programs, it gives the other party the chance to say we're back to the old tax-and-spend ways."

DNC Executive Director Brian Lunde said the report also indicates that, one year after giving him a landslide reelection victory, "The public has moved beyond Ronald Reagan. They have put him in the history books, and they are already into a post-Reagan era . . . . A new discussion about the role of government is waiting to be started."

Burger said Reagan has lost much of his political relevance because he did not run in 1984 with a sharp, well-defined agenda, as he had in 1980. He said that, given the president's continued high popularity ratings, it would be foolish -- and unnecessary -- for Democrats to run against Reagan's record in 1986. He predicted that the 1986 election will not be a referendum on the Reagan administration, as 1984 was, but the first test of the post-Reagan era.