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Daily Kos: Polls in Colorado May Not Be Telling Full Story

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All eyes this election season are on the country’s super-competitive Senate races, which will determine the oft-debated question as to whether Democrats will retain the upper chamber after November.  One of these all-important Senate races is in Colorado, where Republican challenger Cory Gardner has been putting up a small but consistent lead in polls.  As a post at Daily Kos reminds us today though, polling in Colorado from the last few years hasn’t been the most dependable, partly because a number of outfits don’t adequately weigh minority voters.  As Daily Kos Elections puts it:

In 2010’s Senate race, the majority of polls put Republican Ken Buck in the lead (he lost narrowly to Michael Bennet), while in the 2012 presidential race, a number of polls put Mitt Romney in the lead, even though Barack Obama went on to win the state by more than 5 points.

The post calls a recent Colorado polls into question:

We’ve had several developments in the last few days that further call the reliability of Colorado polling into question. One was that SurveyUSA, one of the more reliable pollsters and also one that works to incorporate new technologies, issued two different polls of Colorado from the same timeframe, one on behalf of the Denver Post and the other on behalf of High Point University. What’s most interesting about this is that the two polls used different methods; both were a mix of robo-dialers and online contacts, but the Post poll used random digit dialing and the High Point poll used registration-based sampling (which relies on voter files).

Registration-based sampling is often considered a better approach, since it lets you zoom in on people likelier to vote instead of casting a very broad net. However, the random digit poll captured a larger, and seemingly more accurate Hispanic population; it had a 16 percent Hispanic component (in line with the 2012 exit polls, where Latinos were 14 percent of the sample), while the RBS poll only was 6 percent Hispanic.

Part of the problem is that voter registration in Colorado doesn’t include race (because it isn’t subject to Voting Rights Act preclearance), so the RBS poll’s sample couldn’t be weighted to race. Another potential problem, though, is the RBS poll’s rigorous likely voter screen, which would require a voter to have voted in both 2010 and 2012 or to have registered since then; that could exclude a lot of voters who might not vote with regularity but who will be voting this year (thanks to nagging from Democratic GOTV efforts … and, more importantly, thanks to the fact that this will be an all mail-in election for the first time, which makes voting less of a hassle and boosts turnout, if turnout in Oregon and Washington elections is any indication).

There wasn’t a huge difference between the results of the two polls; the random digit dialed poll found Gardner leading by 2, while the registration-based sample poll found Gardner leading by 4 (which is similar to other findings from RBS pollsters, like CNN’s Wednesday poll, which also put Gardner up 4). However, the RBS poll also found an unusually Republican-friendly Hispanic subsample, with Mark Udall leading only 52-31 among Hispanic voters.

It also lifts up this week’s Latino Decisions poll, which specializes in accurately predicting Latino vote turnout:

Conveniently, another Colorado poll came out on Tuesday as well, which further casts some suspicions on the RBS poll. It’s a poll of only Hispanic voters in Colorado, conducted for the NCLR Action Fund by the pollster Latino Decisions, who specialize in polling Hispanics. The poll was a mix of cellphones, landlines, and Internet, and, unlike most other pollsters, was conducted in either English or Spanish by bilingual interviewers. It found that 14 percent of the electorate is Hispanic (suggesting the random-dialed poll got that right), but also that the Hispanic electorate is breaking much more heavily for Udall than SurveyUSA found: 66-17, with leaners pushed. It also found less of an enthusiasm gap than you’d think, with 43 percent saying that they’re more enthused to vote in 2014 than they were in 2012 (compared with 34 percent saying they were more enthused in 2012).

The bottom line?  Some Colorado polls need to be taken with a grain of salt:

Put this all together, and we’re not very convinced that the bulk of the pollsters looking at Colorado are getting this race right. If the race weren’t especially competitive, none of this would matter, but if it’s the difference between, say, a 1-point Gardner win and a 1-point Udall win, it makes a major difference in calculating the Colorado odds. And with Colorado one of the linchpin races (along with Iowa and Alaska) that could determine Senate control, you can see how that uncertainty just gets amplified when calculating the overall Democratic odds!