Public opinion polls are perplexing. The same is true nationally as in Minnesota and the polling on the state’s two constitutional amendments demonstrate some of the difficulties in doing survey research and public opinion polls these days.
On Sunday the Star Tribune released survey results on the two constitutional amendments. It found that with the Marriage Amendment (to further ban same-sex marriage even more than it is banned in the state by Court decision and law) support for it was at 49%, opposed at 47%, and 4% undecided. For the Elections Amendment to require photo ID at the ballot (and with that effectively to sharply limited if not eliminate election day registration), support for it was a 52%, opposition 44%, and undecided at 4%.
What are we to make of these polls? Are the numbers accurate? Perhaps, but the Star Tribune poll is in need of some qualifications and corrections.
First, look at the poll. It has a margin of error of 3.5%. In itself this margin of error is not bad, but the poll also indicates that for subgroups such as party affiliation the margins of error are larger than that. Again, no surprise that a poll of only 800 respondents would have more error in tabulating results for subgroups. But what is more interesting is the partisan breakdown of the poll-- 41 percent Democrat, 28 percent Republican, and 31 percent independent or other–and the landline versus cellphone population–80% versus 20%. But of these numbers could skew the survey in critical ways.
Consider first partisan affiliation. The survey may have overpolled Democrats and undepolled Republicans. After the 2008 elections (a great year for Democrats), my estimate was that the state was about 39% DFL, 33% GOP, 10% IP (Independent Party), and 18% other. Following the 2010 election (a great year for Republicans), my estimate was 38% DFL, 34% GOP, 12% IP, and 16% other. It seems hardly likely that DFL affiliation in the state today has risen to a level exceeding the 2008 estimates, even considering disapproval with the Republican legislature and Congress. Similarly, after 2010, it is unlikely that GOP support has dropped to 28%. More likely numbers are something along the lines of 38% DFL, 34% GOP, 11% IP, and 15% other.
Why is the partisan adjustment important? The poll suggests significant partisan polarization for both amendments, with 73% of DFLers opposing the marriage amendment and 71% of GOPers supporting. Similar partisan cleavages also exist with the Elections Amendment. If this is true, take the marriage Amendment support at 49% and opposition at 47%. If DFLers are overpolled by 3% and GOP underpolled by 6%, and if about 3/4 of each party votes in a partisan way, I would subtract about 2.25% from opposition (3% x .75) and add 4.5% to support (6% x .75) and the new numbers are 53.5% in support and 44.75% against. This is beyond margin or error.
If one applies the correction to the Elections Amendment there is about an 80% DFL opposition to it and a similar 80% GOP support for it. Then the polls suggest approximately 56.8% support it and 41.6% oppose.
Now there is a second adjustment to the poll–landline versus cell phone users. The poll had 80% landline. This overpolls this type of user. Some estimates are that as many as 40% of the population, especially those who are younger, rely exclusively on cell phones. Older voters are more likely to support the Marriage and Elections Amendment. Again, there seems to be an age divide with about 60%of older voters supporting the Marriage Amendment and about 60% of younger opposed to it. This skewing needs to be corrected but there are two complications here. First, younger people are less likely to vote than older people. Thus, even if the survey overpolled elderly, the results also have to consider undervoting by younger voters. Any serious correction to the skewing by landline and then by failing to correct for younger people not voting leads to concerns about the survey accuracy, even if it claims to have surveyed likely voter. At the least landline or older voters were oversurveyed by perhaps 10% and younger voters not voting may affect the survey by several percent. Nationally, the gap between elderly and younger voters is as high as 10%, in Minnesota it is much less but still significant. I have no good tool at this time to correct for these two variables, but think they might about cancel one another out. My intuition though is to contend that younger cellphone users who will actually vote are underpolled by at least an overall 2%. If that is true, call it 51.5% of the Marriage Amendment and 46.75% against. For the Elections Amendment, now call it 54.8% in support, 43.6% against.
Two other corrections now need to be made. Support for anti-gay initiatives is underpolled compare d to final election returns. Why? People lies to pollsters. In the 2008 California Prop 8 battle, the last survey revealed 47% supporting repeal, with the final election results being 52.24% This is a difference of 5.24%. In Maine in 2009 the last poll prior to repealing its gay marriage legislation yielded an underpolling of 4.9% comparted to the final election results. Yes public opinion might shift, but my estimate is that polls underestimate support for anti-gay rights legislation by about 5%.
Thus, 55.5% in favor and about 42.% opposed to the Amendment. I am assuming that most of the 4% undecided in the poll vote yes.
However, there is also an issue about constitutional amendment voting in Minnesota. If an individual votes in an election but fails to vote on the amendment then the failure to vote is counted as a no vote. What percentage of the electorate undervotes on constitutional amendments? Going back to 1988 and looking at the last 12 amendments, the undervote averages 4.84%. It ranged from a high of 7.68% to a low of 0%. Why is this important? One needs potentially to subtract 5% from any support for constitutional amendments because some people will vote in the election but not on the amendments. It is possible that there will be a similar 4.84% average undervote on one or both of the amendments, but it is also possible it will be lower because both are politically salient and controversial. My guess is an undervote of about 2%. This means subtract 2% from support and then add 2% to opposition.
So where do we stand after all my corrections?
Yes at 53.5%, with No at 44%.
Yes at 52.8%, with No at 45.6%.
My survey corrections do not include the impact of early voting in Minnesota that has already commenced. This may complicate messaging and moving people who have already voted. However, my argument is that the current polls over/underestimate real partisan affiliation, underpoll younger people (cell phone users), fail to calculate undervoting by the young, anti-gay sentiment, and neglect constitutional amendment undervoting. My result thus suggest a closer vote on the Elections Amendment than polls suggest and a larger margin on the Marriage Amendment. Of course, opinion may change and that is why there are elections. Let us see what happens on November 6.