Southern Democratic leaders, viewing the stark racial voting pattern of Tuesday's elections, are calling for a major reassessment of the relationship of blacks and whites within the Democratic Party.

With 90 percent of southern blacks voting for Walter F. Mondale and 71 percent of whites voting for President Reagan, some older white party leaders expressed fear that Democrats are becoming the party of blacks in southern eyes, and Republicans the party of whites.

Others said adjustments must be made to bring blacks and whites together.

Mississippi Democratic Chairman Steven Patterson said in a letter to other party chairmen that the election "is not so much a refutation of a candidate but of a political party. Our defeat is attributable to two major causes," he said, "the failure of the party to attract young, upwardly mobile baby boom America, and the failure to motivate properly blacks, Hispanics and other members of the Rainbow Coalition.

"We must look at our soul," he said in the letter mailed Friday. "We can only blame ourselves."

Patterson is young and not influential in national party circles.

His letter is significant because of its timing and the manner in which it addressed the major Democratic dilemma in the deep South: how to attract more whites to the party while satisfying the desires of blacks to gain a greater voice in party affairs.

The candidacy of Jesse L. Jackson made 1984 a year of rising expectations among blacks and spread political tension across Dixie as whites continued to defect from the Democratic Party. According to ABC exit polls, 9 percent fewer white southerners voted for the Democratic ticket than in 1980. Blacks supplied more than half of the Mondale vote in the South.

There was a familiar ring to the remarks of many older white Democratic leaders in the region. Many interpreted the election as a signal that the party is out of touch with the region's conservative mainstream and too beholden to special interest groups.

"We ought to be just as concerned with the farmer on the tractor as that guy with an earring in his left ear," said one party kingpin.

The largely unspoken inference was that the Democratic Party had become too closely identified with blacks and other minorities.

Alabama Gov. George C. Wallace, one of the South's most durable political figures, called on the party to "start paying more attention to the average citizen and to begin to reflect the thinking of those who work for a living, pay the taxes, fight the war and hold this country together."

Some blacks, their aspirations heightened by the Jackson's candidacy, regard such remarks as racial code words. They look at the election differently and complain that white voters have not adequately supported black candidates. In Mississippi, for example, state Sen. Robert G. Clark failed in an attempt to become the first black Mississippian since Reconstruction to serve in Congress.

"We have tried to build coalitions, but we're ignored, except when we're giving," said Johnnie Walls, a Jackson supporter, who complained that not enough whites supported Clark. "We're always giving and never get anything back in return."

"It appears that more and more white voters are aligning themselves with the Republican Party," said Walls, who considered running for the Senate as an independent this fall. "It's just a continuation of white flight. When black people move in, the whites move out."

"I don't think the Democratic Party can afford to try to out-Reagan Reagan or get as far to the right as the Republican Party is going," said Birmingham Mayor Richard Arrington, one of Mondale's leading black supporters. "The black constituency is so important that it would be suicide to move to the right and alienate black voters, the most loyal constituency the Democratic Party has."

"In all candor, one has to make room for decision-making by minorities, but let it be known that whites are welcome and that we are concerned about the problems of the middle class," said Leslie B. McLemore, a professor of political science at Jackson State University and Hinds County, Miss., Democratic chairman.

No one seems exactly sure how to do that. "There's going to be some creative tension here," said South Carolina Democratic Chairman Bill Youngblood, who has scheduled meetings to discuss racial tension in his state. "We're going to see a lot of finger pointing and breast beating for a while."

Patterson said in his letter that 14 of every 15 Democratic candidates nationally was a white male, adding, "I believe the Democratic Party can no longer ask black voters and Hispanic voters and female voters to elect white men . . . . Nonparticipation at the candidate level leads to nonparticipation at the ballot box."

But the New Deal coalition is no longer valid, Patterson said, adding, "We must let Franklin Roosevelt rest in peace.

"The Democratic Party has become the party of the needy, their platform one of redividing the pie," he said. "But the younger voter wants to be part of a world of growth. The Robin Hood ethic of the Democratic Party this year makes sense only in the confines of a Sherwood Forest that never expands . . . . That world is not the America of personal computers, expanding career opportunities, swifter communication and exploding high-tech industries in which the baby boomers dwell."

The racial polarization of southern vote is part of a trend that dates to the civil rights battles of the 1950s and 1960s when the national Democratic Party became closely identified with racial equality.

Blacks said that Reagan accelerated the polarization and, in effect, encouraged racism by being largely indifferent to civil rights matters. "This administration and Mr. Reagan have sent out certain feelings or vibes that have made some white conservatives feel they're on a roll," said Atlanta City Councilman John Lewis.

But Hamilton Jordan, one of President Jimmy Carter's leading strategists, and others believe that economics, Reagan's popularity and his emphasis on a strong national defense rather than race were what hurt Democrats in the South Tuesday.

He noted that the racial voting pattern in the South was similar to the rest of the country. Nationwide, 88 percent of blacks voted for Mondale; 65 percent of whites voted for Reagan, according to ABC News exit polls. In the South, Reagan got 71 percent of the white vote; 90 percent of blacks voted for Mondale.

"Most folks supported Ronald Reagan because he had a policy which they thought directly benefited them economically," said Steve Suitts, executive director of the Southern Regional Council. "The difficulty is that the policy they saw benefiting themselves harmed blacks and the poor, and white voters were willing to ignore that fact."

He said southern whites also were heavily swayed by Regaan's conservative social agenda. "On 'right to life,' prayer in schools and those sorts of issues, Ronald Reagan symbolized what was important to a lot of white southerners. They voted because they love Ronald Reagan; not because Jesse Jackson scared the hell out of them."