I think another reason for the 50/50 split is the political economics of the first past the post system. If you're trying to win an election and do it without wasting money, you only need to swing 51% or a majority taking into account polling error margins. Every dollar spent on getting more votes is wasted because they're unnecessary to win. This means the overall public being influenced by campaigning naturally falls into a 50/50 with the two main parties fighting viciously for that tiny bit in the center that could go either way.
I think another reason for the 50/50 split is the political economics of the first past the post system. If you're trying to win an election and do it without wasting money, you only need to swing 51% or a majority taking into account polling error margins. Every dollar spent on getting more votes is wasted because they're unnecessary to win. This means the overall public being influenced by campaigning naturally falls into a 50/50 with the two main parties fighting viciously for that tiny bit in the center that could go either way.
FYI-- The light brown color you are using for your titles doesn't stand out very well-- a darker color would make your titles a lot easier to read.