Calling his indictment "garbage," political extremist Lyndon LaRouche Monday claimed Democratic presidential candidate Michael Dukakis orchestrated the charges to destroy La-Rouche's own presidential campaign. "This (the indictment) is purely a political stunt," La-Rouche said. "This is a piece of garbage. I'm not guilty of anything." LaRouche, who was indicted Friday on 13 counts of mail fraud and lying to the Internal Revenue Service, made his accusations at a news conference. He was to be arraigned in federal court in Alexandria, Va., Monday afternoon. Six LaRouche associates were also indicted by the federal grand jury. LaRouche, 66, a perennial third-party presidential candidate known for his outrageous statements, charged Dukakis engineered the indictment as a "dirty trick" aimed at pulling the small number of voters that would have sided with LaRouche to vote for Dukakis.