JACKSON, MISS. -- There are two separate, but closely linked, political contests taking place within Mississippi's fragile Democratic Party.

In one, Jesse L. Jackson has asserted full command over the hearts and souls of black Mississippi Democratic voters, flexing muscles strong enough that he is likely to push aside his strongest challenger, Sen. Albert Gore Jr., of Tennessee, and win the March 8 presidential primary.

In the other, two Mississippi Democrats are engaged in a more subtle struggle that could determine whether the white soul of the state's Democratic Party will be "redneck" or suburbanite. The two, Rep. Wayne Dowdy and Secretary of State Dick Molpus, are vying to be the Democratic nominee in the race to succeed retiring Sen. John C. Stennis.

The presidential and Senate primaries are closely intertwined, producing counterbalancing forces on the electorate. The probability of a Jackson victory on March 8 could increase white participation in the Republican presidential primary that day; the Senate nomination fight between Dowdy and Molpus could keep wavering white Democrats in their own primary.

The presidential primary here offers a clear example of how Jackson's fortunes have changed in four years.

In 1984, Walter F. Mondale capitalized on an arcane caucus system here to turn what had been a tie, or perhaps a Jackson victory, into a 26-to-13 advantage among the state's delegates to the San Francisco convention.

This year, with a primary replacing the caucuses and with none of the white candidates challenging his near lock on the state's black leadership (21 of 22 legislative black caucus members have endorsed him), Jackson is almost assured a plurality, and perhaps a majority, of the Mississippi delegation to the Democratic convention in Atlanta.

"This is Jesse Jackson territory," Mike Alexander, who is managing the state campaign, said.

At the moment, Jackson's strongest challenger is Gore, who is banking on a strong white turnout in northeast and eastern Mississippi, much of which falls within Tennessee's media markets.

Massachusetts Gov. Michael S. Dukakis has put almost no effort into the state, and Rep. Richard A. Gephardt of Missouri, who pulled out his organization earlier to concentrate on Iowa, only now is attempting to rebuild.

Gore's real opposition here may be the Republican candidates, who could draw white voters into the GOP primary. In this environment, Gore strategists are hoping for two things: that the Jimmy Swaggart scandal will discourage potential supporters of Pat Robertson and prompt them to vote Democratic; and that Vice President Bush will score a decisive victory in the March 5 South Carolina primary, diminishing interest in the Mississippi GOP primary.

But Gore has an uphill fight against Jackson, reflecting a pattern of unified black support that has been replicated throughout the South.

Four years ago in Alabama, for example, Birmingham Mayor Richard Arrington and Joe Reed, head of the Alabama Democratic Conference, supported Mondale and siphoned off 34 percent of the black vote for him. That left Jackson with 19.5 percent of the total vote, and he did not qualify for statewide delegates. This year, with Arrington and Reed in his corner, Jackson could lead the field in Alabama. In Georgia, anti-Jackson black leaders in Atlanta are sitting out the race, effectively insuring that no white candidate will get significant numbers of black votes there.

With the Mississippi Democratic Party's black base secured by Jackson, the Senate primary contest could hold the key to the party's future. The outcome could determine whether the party puts together what politicians here label a "redneck-black" coalition in the future or builds on its black base with an appeal to upscale white voters who often support Republicans in presidential and statewide elections.

The Democrat seeking the "redneck-black" coalition is Dowdy, a tough, down-home country boy who says he will "never forget who I am, where I came from or who sent me," and who proudly talks of the endorsement of his cousin, country singer Mel Tillis. It was Dowdy who astonished both Democrats and Republicans in 1981 with an innovative strategy here that won him a House seat in a special election. In the inherently tense biracial Democratic coalition of the 1980s, in which Democrats constantly fear a conservative challenge from the Republicans, Dowdy put together the winning coalition that combined blacks with rural, elderly and working class whites in a district that had been held by Republicans for 10 years.

In the campaign, he supported an extension of the Voting Rights Act and legislation to provide food stamps for striking union members. Once elected, Dowdy successfully promoted legislation to name the new federal building in Jackson after Dr. A.H. McCoy, a black former president of the NAACP, and cosponsored the bill making Martin Luther King's birthday a holiday.

But while Dowdy has been on the cutting edge of the racial revolution in Mississippi politics, he has not been a central figure in the separate drive by another wing of the Democratic Party -- known as "the boys of spring" -- to eliminate corruption among county supervisors and to pull Mississippi's education system up from dead last in the nation.

This group has been led by newly elected Gov. Ray Mabus, along with Molpus and David Crews, who is now managing Molpus' Senate campaign. All worked in key jobs in former governor William Winter's administration. In 1983, Winter successfully restored compulsory education, which segregationists had eliminated after the Brown v. Board of Education decision in 1954, and established the first system of public kindergartens in the state's history.

Mabus' 1987 gubernatorial campaign, which drew on these reform themes, produced a winning coalition strikingly different than Dowdy's. Mabus lost rural counties that Jimmy Carter carried over Ronald Reagan in 1980, and he owed his election to support he gained in the seemingly Republican counties along the Gulf coast where President Reagan had crushed Carter in 1980.

Molpus has developed campaign themes -- "There is a new day dawning in the state,"and "A senator for the new Mississippi" -- designed to play into this reform framework.

The result is a senatorial primary fight in which the two leading Democrats are committed to seeking black support, but have a conflicting image of the white voters who can produce a winning coalition.