Just curious, why is the concept of absolute majority not used a criteria? For example, to win an election in India, you require an absolute majority (if there are 3 candidates and A wins 40%, B wins 30% and C wins 30%, A is still not a winner because a total of 60% voted against A). I see it in this election and in the Brexit vote, a major decision is based on a simple majority with <5% difference.
I think its the other way around, there's a dominant two party system because of the simple majority requirement. If there's a requirement absolute majority, then neither major party wins and the smaller parties and independents that are currently considered spoil sports become very important to form coalitions. That then gives rise to more parties catering to specific interests, demographics and minorities which enable more representation in the senates/parliaments fighting for their primary causes, instead of having to choose either of two always, and any other option basically relegated to a spoil sports.
