DES MOINES -- Jesse L. Jackson peered over the lectern at an audience of 1,000 Iowa bankers and began with a confession. "I'm nervous to the bone," he said, feigning stage fright, "about appearing before such a rich and prosperous group."

No one believed him; no one was supposed to. The wall-to-wall grin gave it away.

Jesse Jackson was yanking their chains (and his own), teasing away stereotypes, advertising ease and command in an unfamiliar setting -- and getting right to the nub of the message that underpins his second bid for the presidency.

It is this: We may have preconceived notions of one another, we may be old adversaries, but we're all in this together now -- all victims of structural changes in the world economy, of corporate avarice and of a government that won't protect us from either.

"Everybody is the same color, in the dark," Jackson told them, delivering the coda of his 1988 campaign.

F. Scott Fitzgerald once wrote that there are no second acts in American lives. Jackson, who will formally declare for the Democratic nomination next Saturday, thinks otherwise. Ever since the end of his 1984 bid, he has been working to recast his image and broaden his base by shifting the locus of his grievances.

It no longer makes sense, he says on the stump, to dwell on "yesterday's fights" about racial injustice. Today's battleground is "economic violence," and its circle of victims is much wider.

"We need to redefine relationships," he told the bankers. "It's not liberal versus conservative, left versus right, or black versus white. It's the Darwinian ethic of the big eating up the small."

In the 45 minutes of speechmaking and questions-and-answers that followed, Jackson painted an economic landscape filled with the "unchecked greed" of multinational corporations that export jobs to "slave labor" markets abroad; with the "huge profits and quick fixes" of the "big money center banks of the East and West Coast and Chicago" that recycle petrodollars into the pockets of foreign dictators; with defense contractors that earn billions in profits but pay no taxes; with a government more interested in deregulating the economy for the rich than in preventing the loss of 38 million jobs since 1973 and 482 bank failures since 1982.

"I submit to you, my friends, there is nothing wrong with the community banker . . . . There is something wrong with the system."

Economic populism and brotherhood-of-victimhood appeals are hardly the usual luncheon fare at a bankers' convention, and Jackson's reviews afterward were mixed at best. He is too sensible a politician to expect to have enlisted anyone in this particular audience in his Rainbow Coalition -- but the mission is to pierce expectations wherever he goes. "I don't think it was what anyone expected," John Chrystal, a prominent Des Moines banker, said of the speech.

Ann F. Lewis, a friend and campaign adviser, says Jackson has been making the difficult passage from being seen as a "protest candidate" in 1984 to a "message candidate in 1988."

Nationwide polls suggest he is making a start in changing public perceptions -- but only a start. A Washington Post-ABC News survey taken late last month showed that his support remains predominantly monochromatic -- 63 percent of black Democrats and only 10 percent of white Democrats back him for president.

But the data also showed that people's negative feelings toward Jackson are down by about one-third and that while he has not yet turned old antagonists into supporters, he is at least better-positioned to get a hearing from them. His favorable-unfavorable ratings are 41 to 30 percent among all voters of both parties, compared with 38 to 46 percent last spring, roughly where it had stood for the previous three years.

The Post-ABC poll showed -- as has every nationwide survey taken since Gary Hart dropped out of the race in May -- that Jackson leads the Democratic pack. In the poll, he had 23 percent of the Democratic vote.

When political professionals point out that his standing is a function of his high name recognition in a field of unknowns, he accepts the analysis but cannot resist tweaking those who would dismiss his achievement.

"They say I'm leading in New York because of high name recognition," he told a mostly black and Hispanic Labor Day rally in Brooklyn. "I'm leading in California because of high name recognition. I'm leading in North and South Carolina because of high name recognition. Well, that's true.

"But I wasn't born with high name recognition!" he said, to the cheers and laughter of the crowd. "I earned high name recognition!"

"Jesse Jackson, your name is No. 1 because of just recognition," he continued. "People don't recognize the stepson of a janitor born to a teen-age mother. If my name was Jesse J. Rockefeller, that might mean something. If my name was Jesse Joe Kennedy, that might mean something. But I'm Jesse Jackson from Greenville, South Carolina, and what does my name mean? My name doesn't mean money. My name doesn't mean oil. My name means service."

He then launched into a recitation of his leadership over the past two decades in areas ranging from open housing and public accommodations, to voting rights and registration, to affirmative action, to his missions to release American prisoners held abroad, to his more recent work on behalf of farmers. Between each line of this shouted resume came the shouted signature line: "My name is service!"

Jackson was preaching to the choir. In October 1983, 54 percent of all blacks named him as the most important black leader in America. Now 76 percent of all blacks think he is. No other black figure attracted more than 1 percent in the poll.

The survey also showed:

Jackson does slighty better among black males (66 percent) than black females (60 percent).

Among both blacks and whites, Jackson does better with younger voters than older ones. While 77 percent of black Democrats age 30 or under support him, only 43 percent of those over 60 support him. Similarly, 13 percent of white Democrats under 30 support Jackson; 17 percent of those 31 to 44 support him, and only 6 percent of those 45 and older back him.

Jackson is somewhat more popular among better-educated white Democrats than among all white Democrats. His efforts to attract the white working class -- a key target group for him -- has not so far been a notable success. The same portion of self-described "working-class" whites as all whites said they support him, 11 percent.

In his stump speeches, Jackson mixes old appeals with new ones. Antidrug exhortations remain his trademark, as they have for more than a decade. "Don't pickle your brains in liquor," he told the Brooklyn rally. "Don't put cocaine in your membrane."

At his frequent high school visits, he asks students who are drug users to come forward (invariably, some do), and tells them, "If I am elected president, I will do my share to cut the supply of drugs, but you must do your share to cut the demand for drugs."

Some of Jackson's economic planks are newer. He calls for investing 10 percent of all public employe pension funds into a fund that would be used for housing construction, infrastructure repair and mass transit. He urges increasing taxes on profitable corporations and creating tax disincentives for companies to move plants and jobs abroad. He calls for shifting 4 percent of the federal budget away from military spending and toward education and housing; for targeting federal research dollars toward health care and commercial applications rather than military ones; for a return of land to family farmers who have lost it through foreclosures.

"You listen to him, and he makes a lot of sense," said Larry Hunt, a farmer who heard Jackson speak recently in Pleasantville, Iowa -- where the farming economy has been in trouble for the past five years. "I really feel he was talking to us. We're kind of fighting the same fights he fought years ago."

Many others, of course, continue to view Jackson with suspicion and fear. His relations with Jews, in particular, are strained. In 1984, Jackson's campaign lost much of its claim to moral high ground after it was disclosed he referred to New York City as "Hymietown," and when he accepted the support of Nation of Islam leader Louis Farrakhan, who had made anti-Semitic remarks.

Jackson has since disassociated himself from Farrakhan. He has also met with Jews, trying to improve relations. The results have been mixed. At one breakfast in Los Angeles last month organized by liberal activist Stanley Sheinbaum, and made up mostly of Jews, Jackson "won over just about everybody in the room," Sheinbaum said -- even though he did not back off from his criticism of Israel for trading with South Africa or his assertion that Farrakhan has a right to free speech, even if some of his views are obnoxious.

That same weekend, however, Jackson also met with the Lexington Group, an organization of young Democratic lawyers and entertainment figures, and he angered some in the audience when he privately berated a young black man who had asked him earlier in the formal question-and-answer session whether he had improved his relationship with Jews. The sight of Jackson dressing down his questioner in the corner of the room caused some members of the group to stop checks that they had sent to Jackson's campaign.

Sheinbaum, who was not at the Lexington meeting, said he thinks tensions between Jackson and Jews will abate, but slowly. "There is no doubt that Jesse gets a bad rap from Jews," he said, "but there is also no question that he sets himself up for it."

For his part, Jackson says he has spent the last four years getting to know different cultures better, getting to know the country better, and is upbeat about the distance he has traveled.

Recently he met here in Iowa with members of a peace group, Beyond War, who told him he had come in first in a recent survey they took. One asked whether Jackson had any cause for hope in a world filled with the threat of nuclear destruction.

"I get hope because in my lifetime I went to catch a bus with my mother and the sign above the bus driver's head said 'Colored seat from the rear.' . . . That sign doesn't exist any more. My mother had to pull me to the back. I said I wanted to sit up front. She said, 'Let's go.' She pinched me. It hurt her to hurt me. She was conditioning me to reduced options. Now, from the back of that bus to the front of your poll is a long way and a cause for hope."

Staff polling director Richard Morin contributed to this report.