The PollyVote predicts the two-party vote. It does not provide vote share forecasts for third-party candidates. Instead, third-party votes are allocated proportionally to the major parties.
The main reason is that four of the six component methods –namely prediction markets, citizen forecasts, index models, and econometric models – do not provide forecasts for third-parties. Therefore, it’s simply not possible to directly predict the third-party vote with the PollyVote method of combining forecasts within and across components.
Therefore, Polly stays the course, at least for 2016. That said, the effects of third-party candidates could potentially be large in future elections.
We thus plan to consider ways of handling the problem and perhaps experiment with alternative ways to estimate third-party votes. In fact, the PollyVote has already been used in Germany to predict the vote of seven parties.