California’s Proposition 19, which will legalize, regulate and tax marijuana, is currently winning, 50 percent yes to 40 percent no, according to a new SurveyUSA poll of likely voters sponsored by CBS 5 KPIX-TV.

SurveyUSA 7/8-11
Prop. 19:
Certain Yes 50
Certain No 40
Not Certain 11
(Note: Because of rounding, poll does not always add up to 100 percent)

This is an automatic poll of 614 likely voters with a margin of error of 4 percent. The poll shows a substantially higher preference for marijuana legalization than other recent surveys from Field Research and Reuters/Ipsos , which both had the measure losing narrowly.

Digging deeper in the numbers, not surprisingly, we see that young voters, 18-34, overwhelmingly support Prop. 19 by a margin of 70-22, while voters over 65 oppose it 50-37. Republicans as a whole oppose the initiative, but Democrats and independents favor it by large margins. The race breakdown is the most interesting measure.

Prop 19 Whites Black Hispanic Asian
Certain Yes 50 52 46 53
Certain No 40 24 43 38
Not Certain 11 24 11 9

SurveyUSA does not show a large disparity in support for Prop. 19 between whites and minorities, while the Field Poll found racial minorities significantly more opposed to marijuana legalization than white voters were. For example, SurveyUSA found Hispanics as the racial group least inclined toward Prop. 19 but still showed them supporting it, 46-43. In the Field poll (PDF) on the other hand, Latinos opposed strongly with only 36 percent supporting Prop. 19, and 62 percent against. Field also had only a bare majority, 52 percent, of young voters supporting Prop. 19. But SurveyUSA found 70 percent of young voters planning to vote yes. This is a significant difference between the two pollsters.

I have heard speculation that there might be a slight reverse “Bradley effect,” where some voters are embarrassed to be supporting Prop. 19 and are telling a live interviewer they oppose it. This might explain why SurveyUSA’s automatic poll, without a live interviewer, has Prop. 19 doing better. Looking at the cross tabs, if there is some type of reserve Bradley effect taking place, the likely source is possibly minorities and young voters who don’t feel comfortable telling a live interviewer they support Prop. 19.