PREVAIL does not cater for parties that fail to win a seat in the election. Winning a seat is quite a high bar to clear. Some such parties manage to accumulate a considerable vote either across the country or in a region. In individual seats they may gain a reasonable percentage of the vote but not enough to win. This is a criticism that can be levelled against First Past the Post. Such parties will often fare better under some form of proportional representation.

To overcome this problem a new criterion for election can be created. This is called PREVAIL PLUS. 

How does PREVAIL PLUS work?

With PREVAIL PLUS new seats are created in Parliament for parties that did not win a seat. A party elected to Parliament in this way would be called a Party without Constituency. Each qualifying party would be represented by one MP. The member holding this seat would be called the Member of Parliament without Constituency for the party. The person who is to hold the seat, in the event of it being won, would be declared prior to the election. 

The quota for each elected party would be unaffected by inclusion of parties without constituency. 

The PREVAIL PLUS Criterion

It might be thought that the criterion for gaining a seat under PREVAIL PLUS should be based on the total number of votes that the party received in the election. A seat in Parliament, though, can be won with a comparatively small number of votes. An independent MP, for example, will have obtained votes in their own constituency only. A fringe or extreme party may accumulate a very small number of votes across each of a fairly large number of constituencies and reach a total vote much greater than that needed to win a single seat. Yet it does not seem desirable that such a party be given a seat in Parliament. To limit extreme parties being elected, some countries have a threshold on total vote to be reached before a party can be elected.

Winning a seat requires an accumulation of votes in a single constituency. It is this concentration that provides the safeguard against extremism. What is needed is a way of easing the extent of this concentration. Because the party has not won a seat, it will have to be spread across several constituencies rather than just one. Concentration is measured as the percentage of the vote that the party obtained in the constituency.

The PREVAIL PLUS criterion adopted here is that, when the percentages of the vote that the party achieved across its ten best  constituencies are added together, the total comes to at least 100%. For this to be true the party must have obtained at least 10% of the vote in at least one constituency. This represents a reasonable accumulation or concentration of votes. It is still quite a high bar to climb. It is likely that only a very small number of parties would meet this threshold in any election.

Having additional party seats under PREVAIL PLUS would be a considerable innovation for Parliament in the UK but it is in common use around the world as a means of increasing representation and proportionality. These are known as Mixed Systems. They usually involve two tiers of voting typically for constituency and then for party. The Additional Member System used by the Scottish Parliament is an example. With PREVAIL PLUS, though, voters just have to vote once. 

The role of a member without constituency