IN a state with a history of political surprises, some experts believe the biggest surprise of them all could be right around the corner: David Duke, a former Ku Klux Klan Grand Wizard, could be on the verge of becoming elected governor of Louisiana.Currently a Republican state representative from Metairie, a New Orleans suburb, Mr. Duke is running neck and neck with two other high-profile Louisiana politicians - incumbent Republican Gov. Buddy Roemer and former three-term Democratic Gov. Edwin Edwards - in Saturday's open primary. US Rep. Clyde Holloway, who has the official state Republican Party endorsement, appears out of the running. President Bush has endorsed Governor Roemer, who switched his party affiliation from Democrat to Republican last March. Seven other minor candidates are listed on the primary ballot. Duke is getting the most attention from political observers simply because so much of his support eludes conventional political polling. "It's a wild situation," says Ed Renwick, an election analyst for Loyola University in New Orleans. "Duke has 31 percent in our polls - which, factoring in what we call both hard and soft support for him and the other candidates, puts him in a dead-heat tie with both Roemer and Mr. Edwards. That's pretty dicey." Mr. Renwick said the problem with Duke is that much of his support doesn't show up in political polls simply because many Duke supporters are "in the closet." With his past KKK affiliations as well as his past support for the neo-Nazi movement, Duke is viewed by many as too controversial - even though most polls indicate that a substantial majority of potential voters sympathize with his strong anti-affirmative action and anti-welfare stances. Some experts believe Duke could actually have as much as 10 percent more support than the polls are recording. "There's no way you can say what Duke's absolute ceiling will be," says Renwick. "He surprised us before. It's very possible that Duke could end up not only in first place, but way, way out in front." Duke has surprised the experts before. Last year he ran an aggressive, grass-roots campaign against incumbent J. Bennett Johnston (D) for the United States Senate, garnering 44 percent of the vote, after almost every statewide survey showed him with no more than 35 percent. Susan Howell, a political pollster for the University of New Orleans, says it would be "almost impossible for Duke to get anything near the vote he got in 1990, simply because there are two other popular candidates in the race." But, she adds: "It's really hard to tell about Duke's level of support from the polls. Right now we have Roemer just marginally ahead in our polls, with Duke and Edwards in a tight race for second. I think [that] if Duke comes in second, that would be considered a major victory for him. But he could surprise everyone and come in first." In debates with Edwards and Roemer, it is usually Duke who gets the most applause with his attacks on welfare spending, big government, and affirmative action, which he calls "racist because it discriminates against white people." Duke's followers, who wave their fists in the air with chants of "Duke! Duke! Duke!" also seem to be the most visible, placing blue and white "Duke for Governor" signs along roadsides and arranging dozens of Duke barbecues and picnics across the state. A recent unofficial survey of political bosses and sheriffs in the state showed Duke leading in nearly every single parish (county) in Louisiana. But even if Duke runs first or second in Saturday's primary, he still would have to face his nearest competitor in a one-on-one runoff in December.