<P> In comparison, for electoral systems using proportional representation (PR), small groups win their proportional share of representation . However, in PR systems, small parties can become decisive in Parliament, thus gaining a power of blackmail against the Government--a problem which is generally reduced by the FPTP method, except for parties with a strong regional basis . </P> <P> Scholars rate voting methods using mathematically derived voting method criteria, which describe desirable features of a method . No ranked preference method can meet all of the criteria, because some of them are mutually exclusive, as shown by results such as Arrow's impossibility theorem and the Gibbard--Satterthwaite theorem . </P> <P> Y The majority criterion states that "if one candidate is preferred by a majority (more than 50%) of voters, then that candidate must win". First - past - the - post meets this criterion (though not the converse: a candidate does not need 50% of the votes in order to win). Although the criterion is met for each constituency vote, it is not met when adding up the total votes for a winning party in a parliament . </P> <P> N The Condorcet winner criterion states that "if a candidate would win a head - to - head competition against every other candidate, then that candidate must win the overall election". First - past - the - post does not meet this criterion . </P>

The problems with first past the post voting explained