Voters in Baton Rouge, La., go to the polls May 5 in a presidential preference primary that many observers see as a three-way split between the top contenders for the Democratic nomination.
Jesse Bankston, chairman of the state Democratic central committee, says Walter Mondale, Gary Hart, and the Rev. Jesse Jackson are expected to do equally well in the popular vote.
Because of a complicated formula for prorating delegates, however, the front-runner in the race has no assurances of winning the most delegates.
The primary is the first stage in a process to choose 39 of the state's 69 delegates to the Democratic National Convention in July. Actual delegates will be selected May 19 at party caucuses throughout the state and will be prorated to each candidate on the basis of his popular strength in each congressional district.
A candidate must get at least 20 percent of the vote in a district to qualify for one delegate.
The additional 30 delegates, Mr. Bankston says, will be chosen either by the central committee or by virtue of the political or party offices they hold.
The Republican primary is also May 5, but the only candidate is President Reagan. The ballots of both parties will have room for uncommitted delegates.
With most of the principal black leaders in the state behind him, including New Orleans Mayor Ernest (Dutch) Morial, Mr. Jackson is expected to do extremely well among minorities. His major concern will be getting his supporters to the polls.
''An organized minority is a political majority,'' Jackson told the first conference of the National Assembly of Black Churches in New Orleans last week.
Jackson supporters are planning a statewide campaign blitz from Shreveport in the northwestern part of the state to New Orleans in the southeast. Sherman Copelin, a New Orleans campaign leader, said Jackson will try to appeal to white voters as well as blacks and has included some whites in his delegate selection list.
Mr. Mondale has the backing of organized labor and some key people close to Democratic Gov. Edwin W. Edwards, who took over the state house in March after unseating the state's first Republican governor, David C. Treen. Governor Edwards himself has not taken a public position on the primary. He is expected to lead the Louisiana delegation to the convention as one of the 30 nonelected delegates.
In a concession to labor, Governor Edwards halted preparations to hold the primary April 7, as originally scheduled. The preparations had gone forward in anticipation of a Justice Department ruling that the election must be held under the 1965 Voting Rights Act. Labor, which has the best political organization in the state, favored delegate selection under the caucus system because of its ability to get voters to the polls.
The Legislature voted in January to suspend the primary, but the Jackson camp complained to the US Justice Department that the action discriminated against blacks. The Justice Department eventually ruled in favor of Jackson, but Edwards attempted to defy the order and Jackson went into federal court.
A federal district judge ruled that the primary must be held and delayed the election from April 7 to May 5.
Secretary of State James H. Brown, a veteran political observer, says that it's entirely possible for Jackson to carry the state by plurality.
The main emphasis of the Hart campaign will be to tell voters about Senator Hart's voting record on energy-related issues, according to State Rep. John W. Scott of Alexandria, the state coordinator for the campaign. Hart positions have been favorable to Louisiana as an oil-producing state, Mr. Scott said.
Organized labor is expected to make a determined effort to get members to the polls in support of Mondale. Shelley Beychok, state campaign coordinator for Mondale, said the former vice-president probably will campaign in Louisiana.
Secretary of State Brown said the delay in holding the primary may actually improve election turnout because of increased national interest in the primary. He said that a number of factors, including the close race at the national level and the publicity over whether the primary would be held at all, have stimulated public interest in the election.