If a broker-oriented black presidential candidacy is to succeed in 1984, its strategists probably will have to convince southerners such as Joe L. Reed of Montgomery, Ala., that they have built a better political mousetrap.

Reed, a city council member and chairman of the Alabama Democratic Conference, the influential state black caucus, has played presidential politics his own way and won.

In 1976, he and other Alabama blacks threw their support to candidate Jimmy Carter. After Carter was elected president, the Alabama blacks, working with the state's regular Democrats, used their access to the new administration to help two young black civil rights lawyers gain lifetime appointments as the state's first black federal judges.

When Reed is asked his opinion of a national, black, favorite-son candidate running in selected Democratic primaries to win black votes and then serve as a broker at the Democratic National Convention, his reply is generally noncommittal, yet firm on one point.

"I can tell you who's going to be the black Alabama brokers," Reed said. "It's going to be black leaders of Alabama, black Alabamans."

Reed's reluctance to relinquish the bargaining role on behalf of blacks in a state that only two decades ago symbolized die-hard segregation is not unique among southern black Democrats.

It is also only one of several problems facing a small, ad hoc group of civil rights leaders and national black politicians as they try to gather grass-roots support in the South, the nation's richest black political soil, for their notion of a black presidential candidacy.

Interviews with nearly three dozen key southern Democrats, blacks and whites, found recently that many are generally leery of any effort that would shift votes from a potential winning candidate to a potential broker or that could splinter black-white coalitions that have helped blacks achieve unprecedented prominence in southern politics.

The black leaders interviewed shared with the planners of the potential candidacy a feeling that national government generally has turned its back on blacks and that the Democratic Party at all levels sometimes takes blacks, its most loyal voters, for granted.

They also acknowledged that conditions for many blacks in the South, despite the huge increase in their numbers, have not improved. These and other factors, they said, could prompt many in their communities to support a black presidential candidate.

"If a real good-looking black candidate came out, we would have a hard time keeping a big segment of our population in this state hitched to the Democratic Party," said Ed Cole, a staff assistant in the Jackson office of Sen. John C. Stennis (D-Miss.) and vice chairman of the state Democratic Party.

Yet southern black Democrats have been told little about the plan so far and, while most are quick to support the principle of a black candidacy, most expressed uncertainty about how well it would work.

"If there was one specific agenda that made a great deal of sense, I would say, 'Yes.' However, there is no such black agenda," said state Sen. Henry E. Braden IV of New Orleans, a member of the Democratic National Committee.

"The problem we had in sloughing the black agenda off the front burner is with the Republicans," Braden said. "The way you correct that problem is getting rid of Mr. Reagan, not weakening the chances of electing your Democratic nominee."

Cole said he is concerned about cutting federal spending for defense, an issue that planners of the presidential effort have emphasized, but he also wants more defense contracts in Mississippi that would provide jobs for black residents.

"While I'm very sympathetic with the concerns of the brothers in New York, I think if we can begin to do some things in the South, we could alleviate some of the problems that they've got up there," Cole said.

Lucius D. Amerson, sheriff and Democratic Party chairman in Macon County, Ala., said, "Many people face reality on this thing. They know that from a national viewpoint, a black probably couldn't muster enough support to get the nomination . . . . They want to vote for somebody who can win and be responsive."

"At this point in time," said Lavonia Allison, chairman of the North Carolina Black Leadership Caucus, "we need not dissipate our energies trying to determine if we have to move in the direction of a candidate. We have to get our act together and say, 'These are our concerns,' in terms of all the candidates."

Black elected officials are key players in the 1984 political drama, and half of the nation's more than 5,000 black elected officials hold office in 11 southern states, stretching from southern Virginia around the cotton and tobacco belts of the southeast to eastern Texas.

With some notable exceptions, such as Mayors Andrew J. Young of Atlanta, Richard Arrington of Birmingham and Ernest N. Morial of New Orleans, most black southern Democrats are small-town mayors, city and county council members, school board representatives, sheriffs and state legislators.

These 11 states contain 56 of the 86 congressional districts where blacks comprise 20 percent or more of the electorate. But only two of the 21 blacks in Congress--Democratic Reps. Mickey Leland (Tex.) and Harold E. Ford (Tenn.)--come from these southern states.

The southern states are critical to any national strategy because in many instances Democratic National Convention guidelines stipulate that a candidate must win at least 20 percent of the vote in a congressional district to win a delegate to the convention from that district.

Moreover, population shifts have resulted in allocation of more delegate seats to southern states, and more southern states are holding primaries and caucuses earlier in 1984.

Georgia and Alabama will have primaries next year on March 13, a "Super Tuesday" of 11 primaries and caucuses in states with nearly 700 convention delegates at stake. Mississippi and South Carolina caucuses are scheduled four days later.

Much of the sentiment for a possible black candidacy has been generated because of the Democratic Party's inability to unite behind Rep. Harold Washington (D-Ill.), winner of the party primary for mayor of Chicago but only a slim favorite to win the April 12 general election because many city Democrats have said they are reluctant to vote for a black.

Southern blacks have seen this happen. Last July, lawyer H.M. (Mickey) Michaux Jr. of Durham, N.C., won a three-way primary for Congress but lost the runoff to a white opponent who had finished 14,000 votes behind Michaux in the primary.

In November, Mississippi state Rep. Robert G. Clark won the Democratic nomination for a congressional seat in an overwhelmingly Democratic district but lost to a white Republican in the general election.

Both contests are part of the litany of betrayals cited by planners of potential black candidacy.

Despite numerous independent campaigns, most of which failed, blacks increasingly have become involved with state party organizations. In some instances, they have supported white Democrats over black independents in areas where they felt the white had been responsive and was more likely to win.

"The mere fact that a black runs does not mean that the Alabama Democratic Conference would support him," Reed said. "The door is not any more wide open for a black than for a white candidate."

Among those interviewed who voiced strong support for a possible black presidential candidacy was Alabama state Sen. Michael A. Figures of Mobile, who complained that southern blacks can rarely win election to office where the electorate is not predominantly black.

"I don't know of any way to break that except to get out and challenge these established structures, especially in the Democratic Party, which has taken us for granted," Figures said. "If one runs, we're going to support him."

Most of those involved in the ad hoc group considering the black candidacy are not from the South, and Atlanta Mayor Young, the most prominent black elected official in the South, has said he opposes a black presidential candidacy.

Leslie B. McLemore, chairman of the political science department at predominantly black Jackson State University, said that even though "basically, black people would rather vote for an attractive black candidate than any white candidate," Young's view is infuential.

Other factors that could draw more southern blacks away from a possible candidacy include emergence of a white candidate or candidates whose stand on various issues affecting blacks would be considered satisfactory.

"If someone comes out and runs the risk of alienating another part of the population for some of the concerns that I have, I would hate to destroy his chances by sponsoring a black candidate," said Fulton County Commissioner A. Reginald Eaves.

Another factor could be the outcome of Chicago's mayoral election, the cause celebre of disgruntled black Democrats.

Asked if a Washington loss would enhance the possibility of a black presidential candidacy in the South, Georgia Democratic Chairman Bert Lance, budget director in the Carter administration, said, "Strike off the words 'the South,' and I'll give you a Jimmy Carter answer: Yes."