Neither Ronald Reagan nor Teddy Kennedy has made any promises about 1984, and even Fritz Mondale's occasional sallies could hardly be called campaigning.

But the candidates for bishop of the African Methodist Episcopal Church, whose election year coincides with national presidential elections, already are on the hustings. The 10,000 delegates to the church's biennial lay convention here this week found themselves besieged with campaign buttons, banners, flyers and a variety of mementos, all urging support for one candidate or another for bishop in an election that still is three years away.

"Go With Bryant The Spiritual Giant" read the bright yellow and blue buttons being pressed on conventioneers by men and women in gold Bryant T-shirts pleading support for their pastor, the Rev. John Richard Bryant of Baltimore's 4,000-member Bethel AME Church.

Supporters of the Rev. Dr. Robert Pruitt, pastor of the local Metropolitan AME Church, dispensed memorial albums of the choir of Metropolitan, which the denomination recognized as its "cathedral church." Pruitt lost last year by an agonizing 40 votes.

The Rev. Lovell Johnson of St. Mark AME Church in Milwaukee sweetened his straightforward campaign pitch -- "Help the Church Grow with Johnson" -- with shiny red apples, boxes and boxes of them.

Churches of the different branches of Christendom follow different traditions in selecting their leaders. In the Roman Catholic Church, bishops are appointed by the pope on the recommendation of the apostolic delegate or papal legate of the country concerned. Since the Second Vatican Council, the counsel of priests and lay members increasingly has been sought in the selection of bishops, but the final decision still comes from the top.

Episcopal Church bishops are elected by delegated bodies of the diocese where the vacancy exists. So are Lutheran bishops, who until very recently in this country were known as synod presidents.

United Methodists have a rather complicated system in which bishops, who in this country are elected for life, are elected at the quadrennial meetings of nine geographic jurisdictions and then assigned to a particular conference (diocese).

There is a certain amount of discreet electioneering in all those bodies. Caucuses of blacks, women, Hispanics or Asians will promote a particular candidate, and regional groups will field a favorite son or, in the case of United Methodists last year, daughter.

A man or woman who yearns to be bishop may engage in a fair amount of behind-the-scenes wheeling and dealing. Personal campaigning beyond general glad-handing and sending out hand-written Chirstmas greetings to every voting delegate is considered pushy and may very well work against a candidate.

In the African Methodist Episcopal Church, which was founded in 1787 when blacks walked out of a Philadelphia Methodist church in protest against color segregation, spirited campaigns for the post of bishop are part of the tradition.

One candidate last year, who staged a full-dress press conference at the National Press Club here on his way to the church's convention in New Orleans, estimated his campaign expenses at "over $10,000" for the post that pays $20,000 a year. He lost.

An ecumenical visitor from the United Methodist Church to an AME convention, who had unsuccessfully sought the bishop's office in his own church, was agog at the electioneering in the AME branch. "I went to the men's room," he recounted to his colleagues back home, "and looked up; they even had election posters plastered over the urinals!"

Biship John Hurst Adams of the Second District of the church here in Washington said there are "several reasons" for the intensity of the campaigns. "First, there's the security," he said. "It's for life. Then, in the society in which we function it's a very prominent and prestigious office to occupy. And it's an excellent opportunity for service." He pointed out that the church, which is only six years away from its 200th anniversary, has had only 101 bishops in all that time.

There will be two vacancies for sure in 1984, because of retirements, and possibly more, depending on the outcome of a study to realign structures of the denomination which stretches over four continents. Adams said it is expected that there will be "50 to 75" candidates in the race by convention time.

Adams said there are no particular issues in the campaign other than "leadership, personality, track record and potential" of the candidates.

James Cobb, a layman from Baltimore, had another view. He said he believed that the candidate he was supporting, his own pastor, Bryant, and a couple of others in the running, including Pruitt, "would change things in the church. They would take this politicking out and put spiritual things in."

But first he had to get his man elected. With a flashy satin Bryant ribbon across his chest, he pressed a campaign button and a pamphlet on everyone who came down the escalator, smiling and murmuring: "We'd certainly appreciate your support."