Most PR systems, apart from the compensatory mixed ones, distribute representation to individuaks by using territorially defined districts, just like the ones presently used under “first-past-the post” rules.The only difference is that they have two or more seats attached to them [the number assigned is known as the “district magnitude”.] The threshold for winning a seat in such a district is determined locally and depends on its district magnitude: the higher the magnitude, the lower the threshold an extremist or fringe candidate, like the BNP ones, would have to surpass in order to win a seat. A rule of thumb is: Threshold % = 1 / number of seats in the district plus 1. So, with nine seats assigned to a district such a candidate would need 10% or more of the vote cast in the district. By keeping the district magnitude relatively low, one can create local district thresholds that in most suituations effectively prevent the election of truly extremist candidates.
