The Minnesota Democratic Farmer Labor Party today endorsed Mark Dayton, a principal heir to the Dayton-Hudson retail store empire, for the seat held by Sen. David F. Durenberger (R-Minn.).

Dayton, 35, making his first run for elective office, is a heavy favorite in the Sept. 14 primary for the DFL nomination over former senator Eugene McCarthy. McCarthy, 66, had been expected at the convention, but he stayed in Washington and did not contest Dayton's endorsement by the convention.

Dayton is trying to make the race a referendum on "the failure of Republican economic policies" that he says have hurt Minnesota more than many other states.

He adds that Durenberger has supported President Reagan "in every important respect," an attempt to counter Durenberger's effort to put distance between Reagan and himself, particularly on such issues as Social Security.

In his acceptance speech, Dayton accused the Reagan administration of enabling "the truly greedy" to "waste billions of dollars of taxpayers' money for their own special subsidies . . . . To those who authored them and to those who voted for them, I say one word: shame. There is no other word for it. Shame."

Dayton will have an uphill fight in the general election if he defeats McCarthy. The Minnesota Poll, which Durenberger's managers say matches theirs, found last month that the senator had overwhelming recognition and a "favorable" image advantage. But Dayton appears to be gaining ground with a heavy dose of TV commercials created by David Garth, a New York political consultant.

Ten years ago, Dayton was a Boston social worker. He had taught science for two years in a junior high school in New York City's lower East Side, where he also lived with a black family in a housing-project apartment. While an undergraduate at Yale he was involved in anti-Vietnam war protests that landed him on Richard M. Nixon's "enemies list," a distinction he cites with pride today.

Since 1975 he has worked as a Senate staffer for Walter F. Mondale in Washington, a Carter-Mondale presidential campaign worker in Atlanta and an Economic Development Commissioner in Minnesota.

All but $70,000 of the $1.9 million he has spent on his campaign in the past 17 months came out of his own wealth. Durenberger, on the other hand, has raised more than the $1 million he has spent in the past nine months.

The Dayton-Hudson Corp., a Minneapolis-based company founded by Dayton's great-grandfather, has 900 outlets in 46 states and an annual gross of nearly $5 billion, ranking seventh in its field.

Dayton's wife, Alida, is the daughter of the late John D. Rockefeller III and the sister of Gov. John D. Rockefeller IV of West Virginia, a Democrat.