A coalition opposed to legalizing recreational use of marijuana in California is launching a campaign against a proposed November ballot measure. A coalition that includes former Facebook president Sean Parker and backed by Lt. Gov. Gavin Newsom and the nation's leading marijuana advocacy groups says it has collected 600,000 signatures, a lot more than the 365,000 needed, well ahead of the July 5 deadline. Newsom, a Democratic candidate for governor in 2018, and other supporters of the ballot measure known as the Adult Use of Marijuana Act plan to launch the official campaign Wednesday in San Francisco.