Why election forecasters disagree about who will win the Senate - Vox

Why election forecasters disagree about who will win the Senate - Vox: And even though models like these have performed well in recent years, they're still all vulnerable to the possibility of a broad-based polling failure. "The volume of polling is way lower than it was 2 and 4 years ago, and the quality of polling is problematic," Silver says. "The response rates get lower and lower every year. Pollsters have still been managing to get decent results, but sooner or later, something's gonna break." One particular problem Silver mentions is that "pollsters tend to herd, or copy off each other. Then, instead of having random variation around some mean, you can get weird patterns where you can be right for several elections in a row, and then you might have fat-tailed errors."