SAN FRANCISCO - The influential senior citizen lobby AARP urged its 3.1 million California members and other voters Wednesday to oppose Proposition 78, which would create a voluntary prescription drug discount program for poor, uninsured state residents. AARP opposes the drug industry-sponsored measure because it would make pharmaceutical industry participation voluntary, but supports an opposing measure that would make discounts mandatory if the companies wanted to fully participate in the state's Medicaid program. "There is a danger if Proposition 78 passes that we will see little or no real benefit," said AARP state director Tom Porter. "Discounts will be provided...