A multi-year drought, a changing climate and a growing population might have created the perfect opportunity for the state to pass a $7.5 billion water bond slated for the ballot next month. It’s a measure touted by supporters as a much-needed investment in California’s water supply, which must serve 38 million residents and large-scale agriculture while providing flows and habitat for flora and fauna that have been decimated by decades of poor water management.

Opponents,…