By the end of a busy day here, Ron Lester has the look of a man who has been trying to push fish and chips on a crowd hungry for steak.

"It's hard," said Lester, relaxing in the hospitality suite provided by the Democratic National Committee. "There's a lot of resistance. Right now, a lot of people just aren't buying. . . ."

Lester is an advance man for the Carter-Mondale Presidential Committee. What he and a host of others have been trying to sell here at the 70th annual NAACP convention is the idea that President Carter would be good for blacks in 1980.

Business has not been good.

There have been outright rejections of the administration's product, even after a major pitch Tuesday night by Vice President Mondale.

There have been polite deferrals. "It's too early to make a choice," said many delegates, several of whom eagerly supported Carter in 1976.

There have been kind words of support - expecially among strong church people who believe in things like family unity - for the born-again president.

Mostly, there has been a yearning for steak, for Sen. Edward M. Kennedy (D-Mass.).

Fish and chips may have sufficed in 1976, after what many in the NAACP called a period of political famine. But they say that will not cut it now.

Man, Carter just hasn't delivered to blacks," said delegate William T. Parker after hearing Mondale Tuesday.

"What has Carter done for us after we went and poured out our hearts for him? On the one hand, you still have all of these black people who never had anything before Carter and who don't have anything now. Then, on the other, you've got black folks like me who have struggled and arrived economically who are p-d off with me because of this austerity bull . . .," said Williams, a marketing manager for a West Coast wine company.

Other rejections were less stinging.

"Right now, I don't see how I could go again with Carter," said James Crawford, a printer from Cheran, S.C., and longtime NAACP member, "Carter's just not putting out the effort that Hubert H. Humphrey or John Kennedy put out for blacks. Now, if you ask me about Sen. Kennedy. . . ." Crawford smiled broadly.

However, not everyone here feels that way.

"I don't think you boys are giving Mr. Carter a fair Break," said a black woman, a Baptish who thought it improper to be quoted by name. "I think he's doing his best.

"And besides, we need a good family man in the presidency. I wouldn't vote for Kennedy because his family life is shady."

Still, it was a Kennedy candidacy that was on many delegates' minds, a fact that proved a sore point for the dozens of adminstration people, mostly middle-level management types, circulating at the convention.

"Those of us in the administration, including myself, are somewhat disappointed that the people who have been speaking here at the convention and elsewhere, that these black people do not seem to be as appreciative of the contributions of the administration as we think they ought to be," said Mary Frances Berry, assistant secretary for education in the Department of Health, Education and Welfare.

Berry, speaking at a new conference, said Carter could win the black vote in 1980 on his record as president, if enough blacks bothered to look at it.

Louis Martin, an assistant to the president for minority affairs, agreed.

Carter has appointed more blacks - more than 300 - to federal executive positions and commissions than any other president, Martin said, adding that Carter also has done more for blacks in education, business and the courts, where he has nominated 18 black federal judges. Martin continued with a laundry list of "all the good things," that Carter has done to help blacks, "things that can be documented because they are on the record," he said.

"In the next 18 months, we're going to make sure that black people get to know about what Carter has done for them," Martin said.

"What about Kennedy?" he was asked.

"Who?" Martin asked, laughing. "Kennedy? He said he isn't running."