According to the emails leaked by Wikileaks, the pre-election polls presented in the media used a technique called oversampling to misrepresent the results.

Sources:

• https://wikileaks.org/podesta-emails/emailid/26551
• https://wikileaks.org/podesta-emails//fileid/26551/7326
• https://wikileaks.org/podesta-emails/emailid/15442

Relevant Quotes:

• “I also want to get your Atlas folks to recommend oversamples for our polling before we start in February.”
• “so we can maximize what we get out of our media polling.”
• [For Arizona] “Research, microtargeting & polling projects - Over-sample Hispanics… - Over-sample the Native American population”
• [For Florida] “On Independents: Tampa and Orlando are better persuasion targets than north or south Florida (check your polls before concluding this). If there are budget questions or oversamples, make sure that Tampa and Orlando are included first.
• [For National] “General election benchmark, 800 sample, with potential over samples in key districts/regions - Benchmark polling in targeted races, with ethnic over samples as needed - Targeting tracking polls in key races, with ethnic over samples as needed”
• “The plan includes a possible focus on women, might be something we want to do is over sample if we are worried about a certain group later in the summer."

Interpretation:​

• This is why you see the skewed polls show Clinton +12 when other more accurate ones show Trump +2. The high Clinton ones oversample democrats by a HUGE margin to get desired results (sometimes 20-40% more Democrats sampled). Many are created by organizations that donate to Hillary, and some are even conducted by her own SuperPACs (https://theconservativetreehouse.com/2016/10/11/media-polling-fully-exposed-about-that-nbcwsj-clinton-11-point-poll/#more-123009)!
• They do this to make Republican voters feel discouraged and not come out to vote if they think their candidate will lose.
• Just look at this example in Arizona (https://theconservativetreehouse.com/2016/10/19/about-that-pro-clinton-arizona-polling-narrative/): Clinton +5, but Democrats were oversampled by 34% (58 out of 100 Democrats, 24 out of 100 Republicans)! Unfortunately, the media only reports on the final number, without reporting on the over-sampling.

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