In a move to keep a State Senate seat in the Republican Party’s hands, Robert J. Helbock, the Conservative candidate in a three-way race, announced yesterday that he was withdrawing from the battle to succeed longtime Senator John J. Marchi of Staten Island. Mr. Marchi, a Republican who has held his seat for 50 years, announced earlier this year that he would not run for re-election. Earlier this month, Mr. Helbock, who was a longtime counsel to the retiring senator, was narrowly defeated in the Republican primary for the Senate seat by City Councilman Andrew J. Lanza. Mr. Helbock decided...