'Still a two horse race after all?'

Throughout this election we've been talking about the emergence of multi-party politics. Gone are the days when Labour and the Conservatives used to get 90% plus of the vote; over the last few months we've been talking 7 party politics.

The SNP, UKIP, Plaid Cymru and the Greens joined the Liberal Democrats as viable alternatives to the main two parties. Yet, when we look at the predictions for seats - both in the exit poll and previous polls - the smaller parties don't seem to be breaking through to gain seats.

Take UKIP - the party's polling has fluctuated but they have been getting about 14% of the vote, and yet they are predicted to only pick up 2 seats. Why is this?

The First-Past-the-Post electoral system historically rewards the big parties - giving them more seats in proportion to their share of the vote in order to deliver stable government.

This works fine when the fight is between 2 main parties, but when 7 parties are fighting for representation something doesn't quite seem right with this way of dividing up seats.

How can UKIP and the Greens be getting more popular support but no more seats? And why will the SNP get a huge number of seats in comparison to the other parties on a similar vote share?

The key is the way parties' vote in spread. The SNP have their vote concentrated in a small number of areas which allows them to out poll their opponents. In contrast, UKIP and the Greens have their support spread across the country. This means they find it far harder to beat opponents in specific places.

This is why we so often hear calls for voting reform. The Electoral Reform Society, for example, have been long standing advocates for change. We've only just had a referendum on AV but, if the smaller parties fail to gain many seat it may well come back onto the political agenda in the next few months.