Proposition 19, which would legalize and regulate production and distribution of marijuana in California, is trailing slightly in the two most recent polls from Field and PPP. Both Field and PPP have the No vote outnumbering the Yes vote by seven percent. SurveyUSA has Prop 19 in slightly better shape, with Yes trailing No by only two points, which is unchanged since last week.

Field (PDF) (10/14-26)
Proposition 19 legalizes marijuana under California but not federal law and permits local governments to regulate and tax its commercial production, distribution and sale. Allows people 21 years or older to possess, cultivate, or transport marijuana for personal use. Fiscal impact: Depending on federal, state and local government actions, potential increased tax and fee revenues in the hundreds of millions of dollars annually and potential correctional savings of several tens of millions of dollars annually. (IF ALREADY VOTED) Did you vote YES or NO on Proposition 19? (IF NOT YET VOTED) If the election were being held today, would you vote YES or NO on Proposition 19?
Yes 42
No 49
Undecided 9

(PDF) (10/29-31)
Proposition 19 would legalize marijuana under California but not federal law. It would permit local governments to regulate and tax
commerical production, distribution, and sale of marijuana. Will you vote yes or no on Proposition 19?
Yes 44
No 51
Undecided 5

SurveyUSA (10/26-31)
California voters may also vote on several propositions. On Proposition 19, which would change California law to legalize marijuana and allow it to be regulated and taxed, are you … Certain to vote yes? Certain to vote no? Or not certain?
Certain Yes 44
Certain No 46
Not Certain 10

While the polling is still relatively close, this is not a good sign. For Prop 19 to pass, there will need to be a very large turnout among supporters and young voters who are not being included in the pollsters’ “likely voter” models.

If Prop 19 does outperform the polls and ends up passing, it will likely be the result of some “reverse Bradley effect,” where some voters feel uncomfortable telling a pollster that they support marijuana legalization. While this is uncommon in polling, it is not unheard of. The big pollsters in 2008 all found California’s anti-same sex marriage initiative, Prop 8, losing in their last polls before the election, only to see the measure win with 52 percent of the vote.

Even if Prop 19 does narrowly fail to pass, the margin is still very important. This is a midterm election, which always sees lower youth turnout than presidential elections. This year in particular is expected to have unusually high turnout among older conservatives, which is hurting Prop 19’s chances. The result is a generally unfavorable electorate for the initiative.

Based on the likely change in levels of turnout by different groups, an identical marijuana legalization ballot measure would probably do two to three percent better with the more demographically favorable 2012 electorate. And that is without taking into account the fact that, in general, support for marijuana legalization has been growing steadily every year.