The Democratic National Committee heard two of its southern presidential candidates criticize the party's reputation for big spending and easy promises today, while a black prospective candidate said Democrats were to blame for the barriers to increased black voting in the South.

The Rev. Jesse L. Jackson, professing himself to be encouraged about his prospects for entering the 1984 race, used his appearance before the DNC to demand that the party eliminate the runoff primary provisions in nine southern states that he said keep blacks from winning nomination to statewide office and thereby discourage blacks from voting.

Earlier, Sen. Ernest F. Hollings (D-S.C.) and former Florida governor Reubin Askew, both declared candidates, said Democrats would have to learn to say no to special-interest groups and their pleas for more federal spending if they are going to defeat President Reagan next year.

Sen. Alan Cranston (D-Calif.), plugging his plans for arms control and federal jobs programs, was the only non-southern voice on the final day of the last DNC meeting before next July's national nominating convention in San Francisco.

None of today's speakers came close to matching the audience size or response that greeted the front-running candidates, former vice president Walter F. Mondale and Sen. John Glenn (D-Ohio) on Thursday.

Polls of committee members taken by ABC and CBS gave Mondale roughly a 2-to-1 lead over Glenn, with the other candidates further back. But more than half of those questioned said they were undecided or unwilling to answer.

On a day when southern accents predominated, there were some sharp barbs at the Democrat's best-known southerner, former president Jimmy Carter.

Saying he was tired of being asked to "explain Jimmy Carter," Hollings pointedly remarked that, unlike the former president, he would keep in close touch with the politicians of his party.

"I won't have to go up to the summit and have a malaise after two years," he said in a reference to Carter's Camp David retreat and speech in the third year of his presidency.

Cranston also took an implied swipe at Carter by saying that he would not "take over the Democratic National Committee as a personal reelection vehicle" if he became president.

Askew, in a speech that drew little applause, said that Democrats "must be willing to say no" to the interest groups. He dramatized his willingness to "take risks" by opposing union-supported domestic content legislation, supporting continued military aid to El Salvador, backing competency tests and merit pay for teachers and opposing the unlimited right of abortion.

Hollings, salting his talk with humorous gibes at himself and his rivals, drew a warmer response, but his message was no less stern. Reagan could easily be beaten on his record, Hollings said, except for the fact that Democrats have a reputation for sacrificing "fiscal responsibility" in their competitive eagerness to tell any interest group, "Monkey see, monkey do, anybody ask, I'm for you."

Jackson confined his brief speech to barriers to voting rights in the South, but told reporters later that he left Detroit with a "very positive taste in my mouth" about a prospective September decision on running. He promised that if he runs it will be in the Democratic primaries and not as an independent, and said his race "would expand the party, not divide it."

The announced Democratic candidates tiptoed around the prospect of Jackson's joining the field, but black critics of the Chicago activist continued to sound their alarms.

Hollings said Jackson would "bring visibility to the campaign," adding, with a smile, that his entry might convince people "there's nothing wrong with being from South Carolina--we can run." Jackson was born in Hollings' home state.

Cranston said that as a contender, he was "certainly not encouraging other candidates to get in the race." But he said that a black candidate in the primaries could help defeat Reagan in November, 1984, by swelling black voter registration.

Mondale aide Elaine Kamarck said that as long as Jackson was just a potential presidential contender, working in southern state voter registration drives, he would help Mondale or any other liberal candidate in the primaries.

"Liberal Mondale could actually win Mississippi," she said. "That's why we're not in more of an uproar."

But Kamarck made it clear that the advantage of Jackson's effort would hold "only if his name is not on the ballot."

The DNC's Black Caucus Thursday night encouraged Jackson's effort by passing a resolution saying a black candidacy in 1984 was "more than appropriate."

But Rep. Mickey Leland (D-Tex.), chairman of the caucus, continued to criticize the idea. Because Jackson might draw off votes from the more liberal white candidates, Leland said, "I personally feel the cons outweight the pros. I'd like to see a liberal Democrat nominee."

Detroit Mayor Coleman Young was not convinced. A longtime critic of Jackson and a supporter of Mondale, the mayor said Jackson's candidacy would be "suicidal" for black interests.

"The most important goal is the defeat of Ronald Reagan, and any process that interferes with that is dangerous," Young said.