The decision by Sen. James O. Eastland (D-Miss.) to retire after six terms has opened the political floodgates here, prompting six Democrats and two Republicans to qualify for the first major senatorial contest in Mississippi since 1947.

The June 6 Democratic primary will pit present Gov. Cliff Finch, the frontrunner; former governor Bill Waller; Columbia attorney and unsuccessful 1975 gubernatorial candidate Maurice Dantin; former lieutenant governor Charles Sullivan; Jackson businessman Robert L. Robinson and State Rep. Richard (Sonny) Tedford of Marks. If necessary, a runoff will be held June 27.

Meanwhile, the Republicans will hold their first seriously contested statewide senatorial primary ever in Mississippi on June 6, when U.S. Rep. Thad Cochran (R-Miss.) of Jackson faces state Sen. Charles Pickering of Laurel, who resigned as chairman of the Mississippi Republican Party to make the race.

While party candidates face a deadline today to qualify officially, independents have until Sept. 28 to qualify. Fayette Major Charles Evers, brother of slain civil rights leader Medgar Evers and influential among blacks statewide, has said he intendsd to seek the Senate seat as an independent rather than a Democrat.

Not since 1947, when then-Circuit Court Judge John C. Stennis slipped past stiff competition to replace Theodore Bilbo in the Senate has Mississippi been involved in such a hotly contested senatorial election.

All candidates are projecting a progessive "New South" image similar to the sort that emerged in the early '70s when southern states started electing governors like Jimmy Carter. All are openly courting black votes and are seeking to place blacks in visible campaign positions.

Finch, 51 has been conceded the frontrunner slot because he's a populist incumbent with the most recent and most active patronage system already in place.

But Walter, 51, who was governor immediately prior to Finch, also developed a reputation as a tough-minded, gregarious populist. Waller is more articulate than Finch, who suffers from something of a "Baccinoods" image, but may be drawing from many of the same pockets of popularity as Finch.

The dark horse candidate, to whom several key Eastland backers have moved, is Dantin, 48, a former district attorney. Dantin met with Eastland before announcing his candidacy, but denied this week he has been "anointed by anyone."

The 53-year-old Sullivan, who served as lieutenant governor from 1967 to 1971, is seeking to make a political comeback, having lost races for governor in 1959, 1963 and 1971.

Robinson, who served under Waller as director of the state's industry-seeking Agricultural and Industrial Board, and Tedford, a second-term state representative, are making their first statewide bids.

Meanwhile, Rep. Cochran's decision to vacate his seat has prompted several candidates to seek his position. State Rep. John Hampton Stennis, a democrat and son of the U.S. senator, is considered the leading candidate against two Democratic opponents and two Republicans, John Hinson of Tylertown, a former aide to Cochran, and Gray Jackson, a Jackson stock-broker.