Reuters: Opponents have taken a small lead in the latest poll on a California ballot measure that calls for half the state’s electricity to be generated by renewable sources by 2025, a Field Poll issued on Friday shows. The poll showed support for California Proposition 7 slipping to 39 percent from 63 percent in July. The latest poll showed 43 percent opposed Prop 7, up from 24 percent in July. Eighteen and that 18 percent were undecided. In the July poll, 82 percent of those asked …