Following up my request a reader crunched the numbers (here is his data table) to show the association between supporting supporting Proposition 37 and voting for Barack Obama by county in California:
From what I know this issue really polarized people in highly educated liberal enclaves in the state of California. Many of my Left non-scientist friends supported the measure because of an anti-corporate animus. But, another issue that sometimes came up was transparency and fair play, in a "teach the controversy" fashion. My own contention is on the scientific point there is no controversy.