For President Reagan, 1985 is likely to be remembered as the year of the summit. For Republicans whose horizons extend beyond the Reagan presidency, it may be recorded as the year the GOP decided to stop conceding the votes of black Americans to the Democrats.

Many blacks of a half-century ago became lifelong Democrats for the same reasons as white working-class Americans: Depression poverty and New Deal promise. The social-welfare programs of the New Deal and Great Society indelibly tied many of the children and grandchildren of these voters to the Democratic Party. Alienation between blacks and the GOP became complete in 1964, when Republican presidential nominee Barry Goldwater went "hunting where the ducks are" in the Sun Belt states.

The "ducks" were white, middle-class conservative voters, many of them nominally Democrats, whose growing affluence and vulnerability to high taxes made them receptive to the limited-government message of Goldwater and, after him, of Reagan. It was a message of little hope to most black Americans. At the entrance to the party of Abraham Lincoln, there seemed to be a sign on the door, "No blacks need apply."

In the intervening years, despite attempts of enlightened Republican chairmen to open this door, even blacks who have grown disillusioned with the Democrats have usually avoided casting their lot with the Republican Party. Reagan, the most popular president since Dwight D. Eisenhower, won the support of only an estimated 11 percent of the black electorate in 1984, despite prosperity and a 49-state landslide.

Neither blacks nor Republicans have benefited from their estrangement, and a case could be made that it hasn't helped the Democrats much, either. Politically, Republicans are tempted to ignore the claims of black Americans, and Democrats are likely to take blacks for granted. After their 1984 presidential election debacle, the Democrats deemphasized their focus on blacks and other "special interests" in the hope of competing for white voters who flocked to Reagan.

Black disillusionment with Reagan has provided a disturbing footnote to his governance. Reagan is no bigot, and he has repeatedly made political mincemeat of candidates who have tried to suggest otherwise in their campaigns. But the suspicion lingers that he has little understanding of the problems of ordinary blacks in modern America. This suspicion was a major component of the complaints of "unfairness" that cost Republicans dearly in the 1982 midterm elections.

After that election, some of the South's most conservative Republicans decided to take a different tack. Republicans with statewide ambitions -- such as Rep. Carroll A. Campbell Jr. (S.C.), a probable candidate for governor, and Sen. Thad Cochran (Miss.) -- actively sought black support. Republicans supported extension of the Voting Rights Act, despite administration foot-dragging.

Subsequently, Republican members of the Conservative Opportunity Society, then led by Rep. Newt Gingrich (Ga.), were among the first to recognize that Reagan's toleration of the instransigence of the South African government was a political albatross draped across the back of the Republican Party.

Reagan traveled a greater political distance to impose sanctions on South Africa than he did to reach the summit, largely because of the push from Republican members of Congress and the resonance of their campaign with such administration officials as national security affairs adviser Robert C. McFarlane.

Ratification of the wisdom of competing for black support, rather than conceding black opposition, occurred this month in New Jersey, where Gov. Thomas H. Kean, a Republican, won a majority of the black vote even though his Democratic challenger, Essex County Executive Peter Shapiro, had more than half of the state's black voters as his constituents and had received more than 90 percent of their votes previously.

Kean's victory came on the day that the election of a black, Democrat Douglas Wilder, as lieutenant governor of Virginia proclaimed the passing of the Old South.

The dual messages of Kean's success and Wilder's victory are unlikely to be lost on Republican candidates in 1986 or those who seek to succeed Reagan in 1988. Black voters can no longer be ignored or taken for granted by either party, which is good for them and even better for America.