In a survey, we found evidence that ordinary citizens are more likely to believe in the accuracy of polls that show their favored candidate winning.
We showed 299 respondents a news story comparing two polls that had equivalent methodological quality (in sample size, representativeness, margin of error, response rate, etc.) but with different results. In one, Clinton was ahead 49 to 43 percent; in the other, Trump was ahead by an equivalent margin. Fully 70 percent of respondents recognized that the two polls were equally accurate. But when the others thought one was better than the other, it was almost always the one that favored their preferred party, as shown in the figure below.
Individuals were strongly biased toward evidence that their candidate was winning. The results replicated our earlier results on issue polling.
In fact, people so completely rejected the idea that the opposing candidate could win that they endorsed polling results that favored their candidate even when that poll was objectively questionable.