A National Labor Relations Board decision has given a major victory to a breakaway union vying with the giant Service Employees International Union to represent tens of thousands of California healthcare workers. The board has called for elections to determine who has the right to represent some 2,300 Kaiser healthcare workers employed at various sites in Southern California. An SEIU affiliate currently represents the workers, but the breakaway group filed a petition in February challenging the SEIU. The balloting will give employees a chance to choose between the two unions.