BY ANDRES VIGLUCCI AND DIANA MARRERO

 As the custody battle over Elian Gonzalez nears its end, Miami-Dade County is more starkly polarized than ever over his fate, a Herald/NBC 6 poll shows: Even as Cuban Americans continue overwhelmingly to believe the boy should remain in the United States, blacks and white non-Hispanics have moved dramatically in the other direction, favoring his return to Cuba by equally overwhelming margins.

 So sharply divided are the groups that they agree on little else in the boy's case, the poll shows -- not on U.S. Attorney General Janet Reno's role, not on controversial comments by Miami-Dade Mayor Alex Penelas, and not on U.S. District Judge K. Michael Moore's decision upholding the government's authority to send Elian home.

 ''In 20 years of studying polls in Dade, I have never seen results that set Cubans and the other two groups so far apart on an issue,'' said Washington pollster Rob Schroth, who conducted the phone survey of 1,013 adult Miami-Dade residents for The Herald and NBC 6. ''The contrast is the starkest I've ever seen. It is truly a tale of two cities,'' he said.

 Non-Cuban Hispanics sided with Cuban Americans on most questions, though in far lesser proportions.

 Even as Elian's father, Juan Miguel Gonzalez, arrived in Washington, D.C., on Thursday to claim his son, eight out of every 10 Cuban Americans in Miami Dade in the poll said they were opposed to a swift reunification. By the same margin, they agreed with a demand by Elian's Miami relatives for a full custody hearing in state court -- a proceeding that Reno has ruled is legally void.

 FEAR SURFACES

 Poll respondent Juan Carlos Roman, a Cuban American, said he feared that if Gonzalez quickly regains custody, he may return to Cuba with his son without further court proceedings. The government has said Gonzalez can go once he gets Elian, possibly next week.

 ''You're talking about a child who has gone through hell. To send him to Washington with his father in one shot would be really traumatizing,'' said Roman, 39. ''If he does have to go back, it should be done gradually.''

 Non-Hispanics' responses to the same questions were diametrically opposed to Cuban Americans': 84 percent of blacks and 71 of whites favor an immediate reunification.

 ''I think he should be with his father because it's his father,'' said Samuel Armstrong, 75, who is black, echoing comments from many non-Hispanics who placed a higher importance on paternity rights than political concerns. ''I'm not concerned with the communists, I'm not concerned with Castro.''

 Only on two of 11 questions was there agreement across the board. Most significantly, the idea of physically interfering with Elian's removal proved unpopular even with Cuban Americans.

 A clear majority of all groups, including 56 percent of Cuban Americans, answered no when asked whether demonstrators would be justified in blocking federal agents' path to the Little Havana home of Elian's relatives.

 ''They should protest and do all they want, but it should be peaceful. It should be in silence and they should just pray for his freedom,'' said Carmen Diaz, 65, a Cuban American who opposes Elian's return to Cuba.

 The bilingual poll, conducted Thursday and Friday, found no real change in Cuban Americans' near-90 percent opposition to Elian's return since a Herald survey asked the same question in December.

 But the new results show a major shift by blacks and white non-Hispanics in the opposite direction. Three-quarters of white non-Hispanics and 92 percent of blacks now want Elian sent home, with a 6 percent and 3 percent, respectively, undecided. That compares with 48 percent of non-Cubans who favored his return in December, with 17 percent then undecided.

 PENELAS' FUTURE

 The poll findings may give Penelas, who is up for reelection this fall, cause for concern.

 It showed that non-Hispanic county residents to be keenly unhappy over Penelas' handling of tensions surrounding the case. They rejected both his vow during a televised news conference to deny federal agents help from county police in repatriating Elian, and his attempt to blame any resulting violence on Reno and President Clinton.

 About 90 percent of blacks and 80 percent of white non-Hispanics disapproved of both statements, and the same proportion disapproved of his overall handling of the crisis. Although at least three-quarters of Cuban Americans approved of both statements as well as Penelas' overall performance, non-Cuban Hispanics were split on the three questions.

 ''I'm sorry emotions are running very strong in this case, but I cannot vote for a leader who will not uphold the laws,'' said Mary Stone, 63, a white non-Hispanic who favors Elian's return to Cuba.

 On Friday, Penelas, who contends his words were misinterpreted, pledged that police would maintain order and protect U.S. agents even if a forcible removal is necessary, though county officers would not directly participate in taking Elian.

 Another politician, Vice President Al Gore, also fared poorly in the survey.

 GORE'S MOTIVES

 In the only other question that drew widespread agreement -- whether Gore acted out of sincere conviction in recently proposing that Elian be granted legal U.S. residency -- a large majority of all groups thought the Democratic presidential candidate was only trolling for the South Florida vote.

 For Reno, the onetime elected state attorney for Miami-Dade whose tough stance on Elian's return has drawn vicious criticism from Cuban Americans, the news was predictably mixed: 86 percent of Cuban Americans disapprove of her handling of the Elian case, while non-Hispanics gave her high marks -- blacks approved by 89 percent, and whites by 71 percent.