Remember back to before NZ’s November General Election and the scrutiny of National’s leader and future Prime Minister John Key? He was labeled as ‘Labour-lite’ and centrist; his party was careful not to wage war on some of Helen Clark’s more popular policies; the differences between the two main parties were small, negligible even.

And for those who follow US politics – you must have been struck by the partisan divide in both society and politics between the Democrats and Republicans. It is, in the words of a columnist, ‘The 50/50 Nation‘. Heck, the two camps even have their own separate news channels!

Over in Germany, people ask themselves: What is the SPD doing in opposition? (oops, sorry, the election isn’t for 2 weeks. I meant, Grand Coalition.) They could form a government with the Greens and the Left Party tomorrow!

Discussion of all these issues, and some others which I have speculated upon here previously, can be informed by a powerful, but simple, political science model (originating in economics) called the Median Voter Theorem.

Briefly, the theorem is a model of majority decision making which states that the median voter’s preferred policy will beat any alternative in a vote; in a stronger form it also says that the median voter will almost always get his/her most preferred policy. The rationale behind it is too much for this blog and is explained briefly and clearly here, but the consequences are far-reaching.

Median_voter_modelIf we apply the model to the Left-Right spectrum above, we can come to the following conclusions:

1) if voters cast their vote for the candidate closest to their ideal policy, then the candidate who stands nearest to the median voter will win. In this case, this would be candidate A, who is closest to point M.

2) if the candidates are free to choose their policies, they will choose positions which will place them closest to the median voter’s at M; so candidates A and B will move in the directions of the arrows towards the middle of the graph and the median voter’s preferences will be fulfilled.

The theory puts the median voter in the lucky position of always getting what they want, but it also has other consequences – many more than will be expanded on here, but to go back to the examples above:

Key vs. Clark in NZ: parties will choose policies which are moderate and middle of the road; no wonder that they look so similar.

Democrats vs. Republicans in the US: if parties continue to act as above for many years they could create blocs, each accounting for approximately half of the population (see the column from Mickey Kraus).

The SPD and the Left Party in Germany: parties will be very careful not to take extreme positions which could alienate voters closer to the median.

So there you have it. A brief but hopefully not-too-incomplete rundown of the Median Voter Theorem in five minutes. A simple, powerful analytical tool for analyzing party politics.

I return to the comparison of which parties are represented in the German and New Zealand houses of parliament and seek to draw some conclusions about what influences party representation in Parliament. Drawing on my previous posts, and bearing in mind that this is just a blog and not an academic paper, I put forward three possible factors influencing party success in elections:

1. Electoral System. A very important factor in a party’s success is the rules under which it is playing the political game. Just ask the Greens, who were never represented in the House before the introduction of MMP but have been ever since.

2. Socio-Economic Factors. According to a typical left-right spectrum, this should be the key influence on party formation and influence, with socio-economic groups organising themselves politically in order to represent their interests in parliament. Perhaps the deciding factor behind the lack of a powerful extreme left party in NZ.

3. Political Culture. This is a very difficult concept in political science: Trying to define political culture has been described as being like ‘nailing a pudding to a wall’. However it is a concept which has lasting influence and appeal. It used to be referred to as ‘socialisation’ – the way that people were initiated into the way politics is done in their society. Phenomena like distrust of  ‘Kingmaker’ parties in NZ, caused by negative previous experience with them, can only be put down to something like political culture.

And as for which factor is most important: As you can see from the brief examples above, they all seem to be important – in different ways and at different times.

It might have struck some of you that the SPD (Labour equivalent) in Germany is in what looks like a terrible state: awful results in the EU elections, very low results in polls, etc.

And if we look across to Britain Labour is in similarly dire straits there: awful results in EU elections, new Tory mayor of London, unpopular leader, low results in polls, etc.

Back in NZ at the election last year, Labour took a drubbing from National; is no longer in Government; has an unpopular leader; and is polling badly.

Looking across these three examples of Social Democratic parties in the doldrums, there are any number of parallels that could be drawn: The departure of a popular and powerful leader (Schröder, Blair, Clark); Responsibility for the current financial crisis (all were in Government up to 2007); Lack of a clear direction or new policies; the list could go on.

An alarmist could even point to further countries in Europe which have recently taken a turn to the right, most notably France but perhaps also Italy or Poland, and declare the demise of Social Democracy. However, fun as it is to speculate on the future of a political ideology, I think this would be short-sighted and a little over the top.

Social Democratic parties have the longest traditions of any parties in Western democracies. They have, over long periods of time, shown a great resilience and capacity to reform and adapt to changing political circumstances. The last generation of  European Social Democratic leaders mentioned above are perhaps the best example of this but in recent memory in NZ we also had the Fourth Labour government.

In hindsight the greatest similarity, and ultimately weakness, across these Social Democratic parties will most likely be seen to be that they were all in Government for a decade (or in NZ’s case, near enough).