Innovative policy proposals are always potentially dangerous to those who advance them in presidential campaigns, and the demise of Gary Hart has made even the phrase "new ideas" a term of political derision.

Hart and his "new ideas" were rejected by the Democrats in 1984 in favor of a familiar candidate with shopworn ideas. Eschewing ideas altogether, President Reagan then trounced Walter F. Mondale while murmuring White House happy talk of "It's morning again in America."

But Reagan had a new idea once. It was a last-minute insert in the Nov. 13, 1979, speech in which he announced his candidacy, an insert added in an attempt to freshen up a Reagan speech that had changed little over the years. The idea was called "the North American accord." Reagan said that "if I am elected president, I would be willing to invite each of our neigbbors to send a special representative to our government to sit in on high-level planning sessions with us, as partners mutually concerned about the future of our continent."

The media greeted the idea with a yawn. Few newspaper accounts of Reagan's candidacy gave it much attention, and some television reports ignored it. I once scoffed at the North American accord as a "kind of encounter group among the leaders of Canada, Mexico and the United States." Reagan aides, aware that reporters tend to be as suspicious as politicians of new ideas, reinforced the skepticism by reassuring the media that the rather vague proposal was merely a campaign gimmick.

But it was more than that to Reagan, who tends to say what he believes and to believe what he says. He has been a resident of southern California for most of his adult life, and he has a Californian's view of the reality of Mexico. He promised when he came into office that he would meet annually with Mexico's president, and he has kept his word, even if some of the meetings have not been especially productive. During their recent and largely friendly meeting in Mazatlan, Reagan fought off a post-luncheon nap while Mexico President Miguel de la Madrid droned on during an unusually long toast.

The governmental exchanges proposed by Reagan have not occurred, and there are constitutional or legal barriers to the involvement of foreigners in domestic governmental processes. But the "North American accord" became a symbol of Reagan's goal of forging a hemispheric common market and his idea that the nations of North America share a common destiny as well as common borders. "Our goal must be a day when the free flow of trade -- from the tip of Tierra del Fuego to the Arctic Circle -- unites the people of the Western Hemisphere in a bond of mutually beneficial exchange . . . , " Reagan said in his final State of the Union address.

The most tangible result of this idea has been the U.S.-Canadian free trade agreement now pending before Congress and the Canadian Parliament. Another byproduct is the less far-reaching U.S.-Mexican framework trade agreement signed last year with Mexico and a host of lesser accords that could be vital steps along the path to a North American common market that would be self-sufficient in energy and agricultural resources.

Mexico has made progress, too. For years, Mexican leaders refused even to talk about trade issues with the United States, considering such discussions an intrusion on national sovereignty. But the debt crisis and the collapse of the world oil market prompted de la Madrid to open Mexico's long-protected markets and prod Mexican businesses to become internationally competitive. The climate of liberalized trade is in the long run likely to do far more to protect the United States from any south-of-the-border Marxist threat than all the arms that have been exported to the Nicaraguan contras.

It is perilous to assess any president's legacy while he is still in office, and the final chapter has yet to be written on many of the administration's most important undertakings. But the promotion of free trade and controlled immigration, plus growing cooperation on drug enforcement within the hemisphere, are vital issues on which the Reagan administration has made some beginnings. There is much to be said for a genuine North American accord.

Reaganism of the Week: Told by a reporter that de la Madrid has charged that U.S. demand for cocaine is the major reason for the increase in Mexican supply of the drug, the president said, "Always has been."