A SNP clean sweep in Scotland could lead to a radical change in Britain's voting laws

There's still a week to go until the general election, but prominent political commentators are already floating the idea of changing the fundamental way in which Britain votes, pushing the case for proportional representation versus the current first-past-the-post system for the first time in decades.

Proportional representation is the system in which seats are allocated based on the party's share of the national vote. Right now, the candidate that receives the most votes is elected to represent his or her constituency.

The electoral system change, which has long been championed by the Liberal Democrats, may finally be gaining momentum with the UK's larger parties.

On Wednesday, Conservative MEP Dan Hannan published an article on ConservativeHome raising the prospect of Tory support for a change in how Britain elects its governments. He writes:

During the 1980s, many Tories reached the view that only first-past-the-post made Thatcherism possible. The permanent coalitions implied by proportional voting would, they believed, condemn Britain to sclerosis. This may have been true, but not because of any property intrinsic in first-past-the-post. It just happened that the Right at that time benefited from the Labour-SDP split as the Left now benefits from the Conservative-UKIP split.

Although Hannan doesn't endorse proportional representation, the implication of the article is clear: This election will likely show the country that the current system doesn't work.

The principled argument for proportional representation is fairly clear: The government better reflects the preferences of the electorate as a whole, it removes the possibility of laziness or corruption creeping into "safe seats" where particular parties are almost certain to win irrespective of the candidate, and it prevents any party from having a structural advantage in the system by equalising the number of votes required to win a seat.

As Hannan notes, this view will not be very popular among the more traditionalist end of the party who worry that a more representative system would inevitably result in no party ever being able to secure a majority. Although he claims that it is better to look at this as what is "right in principle" rather than what plays best for "party advantages," we are currently in a position where happily the two are no longer in conflict - and that means something might finally be done about it.

Here's why it's become such a big issue: For decades, Britain's first-past-the-post (FPTP) has reliably returned a majority for one of the country's two main parties. Since the Second World War the system has produced only two hung parliaments (1974 and 2010) in the 18 General Elections that have been held:

However, with a 98% probability that the 2015 General Election will produce the third post-war hung parliament and the first consecutive hung parliaments since 1910, there are growing concerns that FPTP will no longer deliver the seats for stable government. That's mostly a consequence of two features of the contemporary political scene: The decline in the vote share of mainstream parties and the rise in "fringe" parties such as the Scottish National Party, UKIP, and the Greens.

And that is shifting the electoral calculus for the major parties. To see why both the Conservatives and Labour might suddenly revisit voting reform, you can look at the share of votes that each party needs to get to win a seat - Nicola Sturgeon's SNP is poised to wipe out the other parties in Scotland and could become a permanent feature of future Labour governments:

From that chart it is fairly easy to see why the Lib Dems have been so passionate about voting reform, and why the Conservatives and Labour have been somewhat more circumspect on the issue. It's just been very easy for them to keep winning a large number of seats election after election.

Now, however, that the system seems to be providing a structural advantage to a nationalist party that seeks, ultimately, to break up the union the situation has changed.

There is certainly a question as to whether it would be appropriate to change the rules of the game just to disenfranchise a single player and, with Hannan on the eurosceptic side of his party, there is also an argument that he might not be unhappy with the likely biggest winner of such a shift (at least in the short run) - UKIP.

Nevertheless, the question will undoubtedly be raised if we see an inconclusive result after May 7 and especially if the negotiations that follow fail to produce a government with the parliamentary authority needed to pass legislation without a furious last minute scramble for votes. As Victor Hugo observed: "There is nothing so powerful as an idea whose time has come."