HERE’S a fun game to play if you find yourself in the company of two or more politicos: pull the pin on the question, “What is the best electoral system?”, hoist it into the middle of the group, and step back to watch the explosion.

The game concludes when everyone agrees, no matter what the best system is, that First Past the Post (FPTP) is the worst.

The principle of proportional representation must be defended. Some independence supporters are frustrated by a system that awards list seats to Unionist parties and would prefer a return to FPTP now that the SNP would be the prime beneficiary.

This is reckless, shameless, and unprincipled. Discarding electoral fairness for short-term partisan advantage is no way to build a flourishing democracy.

Some still believe that proportional representation was a Labour plot to stop independence. That is not historically true. Labour’s main concern at the time was not to keep the SNP out, but to keep the Liberal Democrats – whose support was needed for the devolution referendum to pass – in.

The SNP committed to proportional representation in its 1977 draft constitution for an independent Scotland, providing that parliamentary elections “shall be conducted by a system of proportional representation so as to secure a fair reflection of the composition of Scottish society, both in general and with particular regard to party preference and to geographical diversity”. The party’s 2002 draft constitution reiterated this commitment and extended it to local elections.

When the Scottish Parliament was established, it was widely agreed that it should not just be “Westminster-on-Forth”. There was a genuine desire, after having been on the receiving end of Thatcher’s blunt majoritarian rule, for a different type of Parliament: a more consensual, compromising, constructive Parliament, able to sustain a “kinder, gentler”, Nordic type of politics. Proportional representation was integral to that vision.

The extent to which those aspirations have been realised is debatable. Culture is stickier than institutions and adversarial politics remains deeply engrained. Even so, proportional representation has worked. It has enabled greater diversity of representation, prevented unmerited landslides, and still delivered stable governance.

But is the current form of proportional representation, the Additional Member System (AMS), the right choice? Or should other proportional electoral systems be considered?

After all, as Lesley Riddoch recently pointed out in an IndyLive broadcast, AMS was a fix, a bolt-on to correct the FPTP system, rather than something thought through from first principles.

There are two basic objections to AMS. Firstly, that it is not understood; secondly, that it creates two classes of member. These are interlaced, since it is the relationship between these two classes of member that is the main cause of misunderstanding.

For example, we often hear that Murdo Fraser “has never won an election”, when in fact he has won five elections – on the regional list – since 2003. The regional list MSPs are no less elected and no less winners, than those returned by constituencies. After more than two decades, and six elections, we should not have to say this.

Single Transferable Vote, used in Ireland and for Scottish local elections since 2007, is the usual favourite of reformers. It is a preferential system that allows voters to rank candidates and for surplus votes to be transferred. The methods of allocating these transfers are opaque and complex; no voter can be sure where their vote has gone, and the result can depend on the order in which the votes are counted. STV also weakens parties, encouraging clientelistic hyper-local politics in which parliamentarians become “brokers” for constituency interests while ignoring national policy issues.

List-PR, previously used for European Parliament elections, would be a simpler, more intuitive, alternative: one vote, for one party, on one ballot paper. It could operate on a regional level (say, 16 regions each returning eight members, allocated according to the d’Hondt formula), but the single-member constituency element would be sacrificed. Whether that matters – whether there is a need to represent place, as well as party – is a matter for discussion.

Back to the game. Unseasoned players will fight for their favourite electoral system, citing its theoretical advantages regardless of practical circumstance or historical trajectory. More experienced players recognise that there is no perfect system.

The AMS system, like other systems, is imperfect. No doubt it could be improved upon. But it is what we have, and it does work. Tinkering would corrode trust; it looks like moving the goalposts.

If we are to revisit the electoral system, we should do so carefully and holistically, as part of a proper constitution-building process. Knee-jerk changes should be avoided while the broader constitutional question remains unsettled.

Dr Malcolm Petrie of St Andrews University is this week’s guest on the TNT show on Wednesday at 7pm