Interesting report from Nate Silver's website. Six polls done in California — three by automated methods, three by human poll-takers. The automated polls show double-digit approval for a ballot initiative to legalize marijuana. The "human" polls all show the measure trailing slightly.
My recollection is that human polling has shown consistent support in Arkansas for medicinal marijuana (a much more popular proposition than legal recreational use).
But about the wide split in results, 538.com writes:
What if voters are more likely to admit their tolerance for marijuana to an automated script, which may create the feeling of greater anonymity? Marijuana usage remains fairly stigmatized in polite society in America, enough so that even liberal politicians like Barbara Boxer, Dianne Feinstein, Jerry Brown and Barack Obama have refused to state their support for legalizing the drug. But as most Americans between ages 20 and 55 have smoked marijuana, they may not consider it such a big deal in the privacy of their homes — or the privacy of the ballot booth.
Hmm. Maybe it's the same with willingness to admit support for certain candidates in robopolling.