2.4 When does combining forecasts work?

While combining is useful whenever more than one forecasts for the outcome are available, the approach is particularly valuable if

1. Many forecasts from evidence-based methods are available.
2. The forecasts draw upon different methods and data.
3. There is uncertainty about which method is most accurate.

These conditions perfectly apply to election forecasting. First,there are many evidence-based methods for predicting election outcomes. Second, these methods often rely on different data. Third, in most situations, it is difficult to determine a priori which method will provide the best forecast at a given time in an election cycle.