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Nevada’s Odd Numbers: The Complexity of Polling in the Silver State

In the past three electoral cycles Nevada has commanded significant national attention due to the state’s status as both a presidential and congressional battleground state.  Yet, despite the Silver State’s increased electoral clout, Nevada remains one of the most difficult states to reliably poll; a consideration that is not without its consequences as flawed polling has shaped inaccurate perceptions about the competitiveness of many high-profile Nevada races.

This was most obvious in 2010 when unreliable public polling drove the narrative that Sharron Angle was a lock to defeat US Senate Majority Leader Reid.  In 2012, public polling fostered perceptions that Mitt Romney was within striking distance of President Obama (Romney lost Nevada by nearly 7%) and that Shelley Berkley had little chance of defeating Dean Heller in their campaign for the US Senate (Heller escaped with a 11,576 vote, plurality win).

In this post, I review public polling for key races in Nevada from the 2008, 2010, and 2012 cycles to assess the degree to which pollsters are able to accurately gauge the preferences of the state’s electorate.  Next, I drill down on statewide public polls released during the 2012 cycle to suggest that some of this bias stems from pollsters’ inability to accurately measure the preferences of the state’s fast-growing Latino population.  Before doing so, however, I summarize the state’s demographic and political idiosyncrasies that make Nevada a polling minefield:

  • Because Nevada lacks a benchmark poll such as the Field Poll in California or The Elon University Poll in North Carolina, polling done in the state is sporadic and conducted by out of state firms using a variety of methodologies.
  • During the past two decades, Nevada has been the fastest growing state in the country and the state has some of the highest rates of annual in and out migration as just 24.3% of residents were born in the state; the lowest share in the country.
  • Better than a quarter of Nevada’s population (27.4%) speaks a language other than English at home and roughly a quarter of adults in live in households that use only cell phones.
  • The state’s largest source of employment, the hospitality industry, necessitates that many Nevadans work and live non-traditional schedules.
  • The economic downturn hit Nevada particularly hard resulting in record foreclosures and significant population dislocation.
  • For statewide federal and state elections Nevada has a “none of these candidates” option and many Nevada elections feature minor party candidates; both of which are often excluded by pollsters.
  • Nevada’s voter registration is highly variable.  Between March and October statewide voter registration increased by 21% and in Clark County, home to nearly three quarters of the state’s population, registration increased by 26%.

In sum, while Nevada has pockets of shrinking demographic and political stability (e.g., the state’s rural counties), Nevada’s ascendant urban spaces are increasingly non-white, younger, and mobile.  As a consequence, polling Nevada is a tall order; a point borne out by the data presented in Table 1.  Specifically, these data compare projected results from publicly released polls in the week or so before Election Day to the results for statewide and competitive House races from the 2008, 2010, and 2012 cycles.  All of these polls were released either during or after the conclusion of Nevada’s absentee and early voting period and all use likely voter sampling frames.  In 2008, 67% of all votes were cast prior to Election Day; in 2010, 60%; and in 2012, nearly 71%.  Thus, the degree to which pollsters make use of this information should improve the accuracy of the projections presented in Table 1.

Inspection of the Table 1 suggests a number of interesting factors at play.  First, because Nevada was perceived as a presidential swing state and it featured a competitive US Senate race and two competitive House elections, there was more polling done by more firms in 2012 as compared to 2008 and 2010.

Second, with the glaring exception of the SurveyUSA poll of Nevada’s 4th House district, polling was generally more accurate in 2012 as compared to 2008 and 2010.  At the same time, pollsters tended to generate less reliable projections for the US Senate race as compared to the presidential election.  One likely reason for this was that nearly 10% of the votes cast in the Senate race went to either a minor party candidate or to the none option (by comparison 98% of the votes cast for the presidency went to either Romney or Obama).  Moreover, throughout the fall there were significantly more undecided and soft supporters in the Senate race as compared to the presidential contest.

Third, in 2012, PPP, a Democratic polling form, performed quite well, while Rasmussen, a Republican polling firm, did not despite that fact the both firms use automated telephone interviews.  However, the worst performing firm in Nevada in recent cycles was Mason-Dixon.  Indeed, because of the firm’s poor performance during 2008 and 2010, in 2012 the Las Vegas Review Journal dropped Mason-Dixon in favor of SurveyUSA.  Of particular note is Mason-Dixon’s final 2008 poll, which was released two days before Election Day and after nearly 67% of the total vote had been cast, that underestimated Barack Obama’s vote share by 8%!

Finally, and most importantly, when the polls miss in Nevada they do so by consistently underestimating Democratic support and/or overestimating the Republican vote share.  This partisan bias is likely due to two factors.  First, the issues outlined above detailing the state’s political demography are more likely to affect constituencies that all-else-equal are Democratic leaning.  Second, as Election Day approaches and pollsters switch from registered to likely voter sampling frames, the exclusion of voters who pollsters judge to have lower probabilities of voting further increases the likelihood that potential Democratic voters will not be sampled.

Some of these dynamics can be seen by examining the Latino sub-samples in the 2012 Nevada public polls.  Specifically, Table 2 summarizes the sample size, margin of error, polling method, estimated Latino share of the electorate, and projected Latino vote preferences for polls that made this information publicly available.  Also included in Table 2 are the results of the impreMedia/Latino Decisions Election Eve Poll and the 2012 exit poll results for Nevada.

Using the estimates from the exit polls and the impreMedia/Latino Decisions Election Eve Poll as baselines suggests that public polling conducted in Nevada in 2012 struggled to accurately capture both the Latino share of the electorate and the candidate preferences of Latino voters.  The consequence of this, even taking into consideration the larger sub-group error margins for these polls, was a consistent underestimation of Obama and Berkley’s support among Latinos and significant variation in pollsters’ expectations about Latino turnout.

This is most evident when comparing the final PPP and SurveyUSA polls.  Whereas PPP included a Latino sub-sample of 14%, the final SurveyUSA poll assumed a Latino vote share 50% larger.  Yet, PPP had a more accurate projection of the Latino vote in both the US Senate (Berkley + 31%) and presidential (Obama +34%) contests as compared to SurveyUSA.  Indeed, despite the fact that over a fifth of the SurveyUSA sample was identified as Latino, the poll projected a 22%margin for Obama over Romney and a one point Heller margin over Berkley.  YouGov’s internet based poll too projected significant drop off in the Democratic Latino vote between the presidential and US Senate races, but estimated a larger margin than the PPP survey for the presidential race (Obama +40%) and assumed that Latino’s would constitute 15% of the vote (as was the case in 2008 and 2010).

Interestingly, even though PPP, SurveyUSA, and YouGov all used different methods and each poll had different estimates of the size of the Latino electorate and Obama’s margin over Romney among Latinos, the actual presidential vote was within the polls’ margins of error.  So, even though all three polls missed the Latino vote to varying degrees, by overestimating the Democratic support and underestimating the Republican vote among other demographic groups, all three firms were able to generate accurate projections of Romney and Obama’s aggregate vote shares in Nevada.

What is less clear is why the polls all projected smaller Democratic margins for the US Senate race.  Specifically, the exit polls projected a 39% advantage for Berkley over Heller and the impreMedia/Latino Decisions Election Eve Poll estimated a 50% advantage.  In contrast, the margins reported by the YouGov, PPP, and SurveyUSA polls were 16%, 31%, and (an implausible) -1% respectively.  Consequently, the two polls predicting the smaller margins (YouGov and SurveyUSA) each missed Berkley’s vote share beyond the margin of error, while either overestimating Heller vote by a negligible 1% (YouGov) or hitting it exactly (SurveyUSA).  To correctly project Heller’s total vote share while at the same time being so far off in projecting his share of the Latino vote required these polls to underestimate Heller’s vote share among other voting sub-groups.

Why this occurs is likely a function of two inter-related factors.  First, cell-phone only, Spanish speaking, lower socio-economic status Latinos who are the most Democratic of all Latinos voters are the most difficult (and costly) voters to include in a poll.  Thus, as addressed elsewhere on the Latino Decisions blog, even if polls include both Spanish language and non-landline sampling frames, they are unlikely to capture a representative cross-section of Latino voters and instead, are likely to over-sample more English speaking, higher income, and Republican leaning Latinos.

Second, screens used by polling firms to determine which registered voters are likely to actually turnout may systematically exclude Latino voters because of their demographics or prior voting records.  There is ample reason to suggest that this occurred in Nevada in 2012.  For instance, an analysis of the final pre-election voter registration file for Clark County (home to 68% of Nevada’s registered voters) conducted by the Ramirez Group, a Las Vegas consulting firm, found an astounding 37% increase in registered voters with Latino surnames between March and October.  Many of these registrants were young, first time voters; the exact type of voters who would be excluded from a likely voter frame.

More importantly, it appears that many voters who pollsters presumed to be marginal voters did in fact vote.  Specifically, an analysis of early voting turnout in Clark County by political analyst Jon Ralston found that half of the 26,000 Democrats who registered after June 1st voted early, as did 40% of Democratic voters who had never voted before. Ralston’s analysis also revealed that Democrats turned out roughly two-thirds of the 20,000 voters from the inactive voting list during early voting.

To be sure, there are pollsters that work in Nevada who generate consistently reliable results.  Most notably, Mark Mellman, who worked for Reid in 2010 and was Berkley’s 2012 pollster, and Republican Glen Bolger, whose last publicly released Nevada poll was in September, are widely respected on both sides of the aisle.[1]  As for other pollsters, until they are able to demonstrate a consistent record of accurately projecting both the composition and the preferences of the Nevada electorate, their results should be viewed with a healthy dose of skepticism.

David F. Damore is an Associate Professor of Political Science at the University of Nevada, Las Vegas and an expert in Nevada politics.

The commentary of this article reflects the views of the author and do not necessarily reflect the views of Latino Decisions. Latino Decisions and Pacific Market Research, LLC make no representations about the accuracy of the content of the article.

[1] To counter the narrative that Berkley was losing badly, Mellman released a poll one month out showing Berkley up 41 to 38.  Subsequent tracking, however, consistently showed Berkley trailing by 1%; the eventual margin.   Berkley, thus, was likely one of the few candidates done in by the negative advertising from both Heller and various outside groups, which relentlessly highlighted her on-going ethics investigation.  Note that Heller received 5,967 fewer votes than Romney, while Berkley ran 84,492 votes behind Obama.  Relative to the presidential race, none of above voting increased by nearly 40,000, as did the minor party vote.  In the waning days of the campaign and knowing that Romney had little chance in Nevada, Heller was quick to tout his support among Obama/Heller voters.  However, it appears that the more likely difference makers were Obama/NOTA voters.  Ironically, Republican operatives had sued to have the “none of these candidates” option removed from the ballot on the grounds that it disenfranchised voters because “none” could not win.  A District Court Judge who graduated from Brigham Young University with Mitt Romney agreed, but his decision way stayed by the Ninth Circuit on appeal by the Democratic Secretary of State, Ross Miller who may have been the Democratic Senate candidate had Berkley opted not to run.


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