Sen. Edward M. Kennedy played preacher today, thumping the podium and waving his hand as he declared before the NAACP's 71st annual convention here that he would keep the faith and not bend to the rightward drift of the nation.

"We must stand against the forces of Reaganism now seeking to replace affirmative action with negative reaction. And we must stand against the apostles of pessimism in the Democratic Party now summoning us to settle for a lesser life in a lesser land," he said.

NAACP members were the perfect reviival crowd, cheering, clapping and some shouting lusty amens.

Much of Kennedy's presentation was filled with reminiscences of his roles in past civil rights wars. But he emphasized he's continuing his battles in "this summer of national discontent" while Carter forces are attempting to compromise with right wing policies.

"There surely is a right wing threat, but I am convinced that we will not defeat it by tilting toward it. Rosa Parks did not win her victory for justice by moving to the middle of the bus," he said.

He was clearly exultant about being able to move Carter forces to more liberal positions in recent party platform fights on such subjects as federal assistance for black colleges, denunciation of the resurgence of the Ku Klux Klan and Haitian refugee policy.

But, he said, he had not been able to move them far enough.

"I am determined to turn what was a minority on the Democratiic platform committee into a majority at the Democratic National Convention," he said. "For me, the issue is not phrases on paper, but people in pain -- people I have seen for many months, in many parts of this land."

Although a majority of blacks supported President Carter in Democratic primaries, the NAACP members who packed a dining room of the Fontainebleau Hotel here to hear Kennedy were widly enthusiastic about the senator.

Several rushed to the front when he arrived to take his photograph. At the end of his speech, they stood and waved yellow luncheon napkins as they sang with him a verse from the song "Lift Every Voice and Sing," which is generally referred to as the Negro National Anthem.

"He just said what was what," said Louise Culberson, an NAACP member from Fayetteville, N.C. "He didn't get up there and use big words. He didn't low-rate anybody."

Ernest Watts, a federal government retiree from Detroit, said, "I don't know anybody who would get up there and tell the truth like he did."

"Carter hasn't done some of the things he promised for blacks," said NAACP member Tommy Walker, a pressman from Lancaster, S.C. "We get millions of youths across the country who can't find jobs." Walker said his son, a recent college graduate, is unable to find work.

Kennedy appeared to strike a chord with the crowd when he talked about the need for national health insurance. Saying black life expectancy is shorter and that blacks are more likely to die of hypertension or kidney failure, he declared: "In America today, being black is dangerous to your health."

And they especially loved it when he talked about the "generous plan" that Carter and members of Congress have for their own medical needs.

"We don't get a bill unless we ask for it and I want to ask you when was the last time a member of Congress asked for a bill," he said to laughter.

Earlier today, Kennedy visited Miami's riot-ravaged Liberty City, stopping first on a lot housing the ruins of a burned down supermarket. It was only a block away from the senior citizens center where Carter's limousine was pelted with rocks and bottles four weeks ago.

The crowd of about 100 that turned out was enthusiastic about Kennedy. A teen-age youth screamed shrilly and shouted, "Bless him, bless him," after Kennedy shook his hand.