In his first major campaign appearance as a candidate for Congress, the trombonist-singer Willie Colon barely shook hands. Instead he was grabbed, squeezed and kissed as he zigzagged up Fifth Avenue on June 12 in the Puerto Rican Day Parade, ambushed by grown women who hopped in excitement after touching him, bearhugged by men who shrieked "Willieeee! Ven aca!" ("Come here!").
Mr. Colon, an international salsa star, announced this month that he will challenge Rep. Eliot L. Engel in the September Democratic primary for the 17th Congressional District seat in the Bronx and Westchester County. His fans were not surprised. For much of his nearly three decades as a musician, Mr. Colon has offered social commentary with a 3/2 Afro-Caribbean beat, railing against military despots, exposing unsavory slices of barrio life, finding inspiration as readily in AIDS as in child beggars in Bogota.
But now Mr. Colon, a 44-year-old native of the Bronx, will test whether a musical appeal that transcends age and gender can carry over to politics, and across ethnic lines. The district is equal parts black, Hispanic and white, and not all of them listen to salsa. Mr. Colon is of Puerto Rican descent.
"I listen to Frank Sinatra," said Paolo Polombo, 51, an Engel supporter and chairman of the Italian-American Federation of the Bronx and Westchester, which represents 20 organizations. 'I Will Vote for Him if . . .'
Said Angel Vegas, 39, a teacher and Colon fan: "I will vote for him if he deals with housing, AIDS, education and unity for people in New York."
Mr. Colon says he was prompted to enter politics by what he views as disturbing trends. One is what he calls a regression in race relations, another misplaced government priorities like cutting back schools and social programs while spending billions in foreign aid.
He says he is also looking for new challenges after his enormous success as a bandleader and record producer. "Sometimes writing a song is not enough," he says.
Mr. Colon, who released his first album at age 16, now has 10 gold albums (a gold album signifies 500,000 copies sold) and 10 Grammy nominations to his name. "Siembra" ("Sow"), recorded with the singer Ruben Blades, has sold more than three million copies worldwide.
Mr. Blades recently pursued his own political aspirations by running for president of Panama (he lost). Mr. Colon says it should not come as a surprise that both he and Mr. Blades wanted to enter politics, since their musical collaboration stemmed from "that confluence of ideas and ideals." Those ideals have led Mr. Colon over the years to raise money for drug prevention, become active in environmental groups and lend his celebrity to the campaigns of President Clinton and former Mayor David N. Dinkins. Wanted: Coalition
In his first try for public office, Mr. Colon says he needs a coalition to win, and political analysts agree. They say the race offers a test of the ability of black and Hispanic residents to come together in city politics, an effort that has often been thwarted by rivalries between the two groups.
Mr. Engel, a liberal Democrat who is seeking his fourth term in Congress, has the backing of the Bronx Democratic organization and won his last primary with more than 70 percent of the vote and the general election with more than 80 percent. His is a scattered district that covers parts of the Bronx, Yonkers, Mount Vernon, Pelham and New Rochelle and includes low-income pockets like the South Bronx, affluent areas like Riverdale and the huge residential complex Co-op City, the Congressman's political base.
But Mr. Engel is a white incumbent facing for the first time a minority opponent in a district redrawn in 1992 to give minority groups greater political influence. The voting-age population in the area is 36 percent black, 34 percent non-Hispanic white and 26 percent Hispanic.
"That district is a microcosm of the citywide challenge to be able to build multiracial coalitions," said John H. Mollenkopf, a professor of political science at the City University of New York Graduate Center. "Neither blacks nor Hispanics are going to be a majority by themselves." Counting on 3 Endorsements
Mr. Colon, who said he has collected the necessary signatures to get a spot on the primary ballot, is counting on the endorsement of three important black leaders -- Assemblyman Lawrence B. Seabrook, City Council member Lawrence A. Warden and the Rev. Al Sharpton, who has vowed to "call on my people to show real unity, above race."
Many familiar with Bronx politics say the black leaders don't think the race is winnable because the district's demographics have not changed enough for black and Hispanic voters to offset the traditional higher turnout of white voters. Instead, they note, black leaders are building alliances with Hispanic voters now for a candidacy in the future.
Mr. Seabrook, who had planned to run but decided against it after being elected chairman of the Black and Puerto Rican caucus in February, denies it. "The numbers are there," he said. "The district was carved out for a minority congressman."
Mr. Colon has high-name recognition and his own financial resources to throw into his campaign. (Mr. Colon estimates he will need to spend $600,000; Mr. Engel plans on spending $200,000.) He says he has the support of Local 1199 of the hospital workers union and District Council 37, the city's largest municipal union. He also has the encouragement of many Hispanic elected officials, although most have yet to publicly endorse him. Talk of Building Bridges
So far Mr. Colon has been vague on issues. He talks about wanting to "build bridges" between ethnic groups and focusing on small community problems that affect quality of life. When asked to name some of the problems during an interview, he answered: "I have an idea of the tone and the kind of representation that the district needs. I'm not going to tell them what their problems are. I want the people in this district to come forward so we can develop a progressive agenda."
Mr. Colon, who lives in New Rochelle with his wife and three sons, calls Mr. Engel "out of touch," but he is reluctant to criticize him. The incumbent seems equally shy. He says he likes salsa and has one of Mr. Colon's tapes, "American Color."
"You can't help living in the Bronx and not liking salsa music and listening to it," said the Congressman, an accordion player.
Mr. Engel, 47, says the issue in the campaign should be his record. He calls himself a "hands-on legislator" who has five offices in the district to address its concerns, helped win a waiver from Federal insurance law that saved the city's public hospitals $500 million last year and has pursued "the working-class" interests of his constituents as a member of the House Committee on Education and Labor and the Committee on Foreign Affairs.
He notes that Mr. Colon became a Democrat just last year after switching from the Liberal Party, and that he votes sporadically and skipped voting for Governor in 1982, 1986 and 1990.
"That's an indication of lack of participation, and that's something," he said.
But few of Mr. Colon's admirers seem worried about his qualifications, and they say that Mr. Colon, a high-school dropout who went on to huge success, knows the vicissitudes of the poor.
"When one has spent much of life on the streets, one knows much more," said Victor Batista, 21, a transit guard who said he will vote for Mr. Colon.
Reginald Fant, a volunteer from Local 1199 who is gathering nominating petitions in black neighborhoods, agrees. "He has the same bumps and bruises," he said. "It's easy to endorse him."
Still, Mr. Colon's electoral strength rests on fans.
Mr. Colon said he had been worried someone would yell out "Where's your trombone!" during the Puerto Rican Day Parade. Until then, he hadn't known what the reaction would be among audiences he now calls constituents.
But many fans flashed him a thumbs-up sign. He thinks they approved.
"A lot of times people don't want to let you make that crossover," he said. "But they were urging me on to do it. They put all doubts to rest."
Photo: Willie Colon is hoping that his popularity as a musician will help him in his race for Congress. He greeted supporters as he marched June 12 in the Puerto Rican Day Parade. (Philip Greenberg for The New York Times)(pg. 25) Graph: "AT A GLANCE: 17th Congressional District" racial and ethnic makeup and results of the 1992 presidential vote for the 17th Congressional Group. (Source: Census Bureau)