This is a method by which you can make your own forecast using two sliders: The Popularity slider and the Opposition Unity slider.
Two factors affect the number of seats the main party wins:
- The popularity of the main party (% votes the main party wins)
- How united the opposition is to that main party. Opposition Unity is measured by the Index of Opposition Unity (IOU) which ranges from 100 (fully united opposition - a straight two party fight) to 0 (totally disunited opposition).
The main party wins more seats if its popularity increases and/or the opposition to it is less united.