I read with interest Professor Patrick Dunleavy's piece on the rise of multipartyism in the United Kingdom. You can read it here. Dunleavy notes that declining support for the Conservative and Labour parties over the past three decades, and the surge in support for minor parties during the same period, is sounding the death knell for Duverger's Law--a "law" that I tell students about in my Introduction in American Politics class to help them understand the lack of third party success in the US election system.
Duverger's Law, in short, says that election systems dictate the amount of party competition in a state. In systems utilizing a winner-take-all, plurality system of elections with single-member, geographic constituencies, two parties are able to dominate the electoral system, squeezing out third parties.
In giving examples of Duverger's Law, I have often pointed as well to the United Kingdom's system of representation in Parliament, which also features winner-take-all, plurality elections with single member districts. But, as Dunleavy rightly notes, the rise of the Liberal Democrats over the past two decades and the more recent successes of national parties in Wales and Scotland suggest that Duverger's Law may explain very little. Maybe electoral systems don't really matter in determining the competitiveness of a party system.
I remain skeptical of Dunleavy's argument that the demise of Labour in Scotland and the rise of UKIP in England and Wales heralds an end to Duverger's Law. I'm also skeptical of his explanation of why the United States continues to have a system dominated by two parties, which hinges on our big money elections, partisan redistricting, and the fact that we don't use alternative vote systems.
I hesitate to tackle Dunleavy on the UK system, as I'm no expert. That said, let me suggest two other factors for the decline of two party support in the UK that do not imperil Duverger's Law. The first is the fact that, with the arrival of devolution and the UK's membership in the European Union, the English, Scots, and the Welsh increasingly find themselves voting in elections without winner-take-all, single member elections. This allows citizens to experience tactical voting and to vote for third, fourth, or fifth parties without "wasting" their votes. It is inevitable that this experience would eventually allow citizens to develop stronger connections to alternative parties, and that these allegiances would be transferred up ballot. In the US, alternative voting systems are rare, in part, because the Supreme Court has repeatedly struck down such systems because of 14th amendment "one man, one vote" concerns and the fact that these alternative voting systems have been used on a discriminatory basis to undercut the voting power of minority voters.
It is quite possible, and indeed probable, that the United Kingdom is going through such a period, after which, two party support will rise again. Perhaps with one or two new main parties displacing Labour and the Tories. Fact is the two issues both parties are struggling to cope with are the rise of nationalism in Scotland (and to a lesser degree, in Wales) and immigration. In part, the two party system is under stress both due to a cleavage issue (immigration) and regional issue (nationalism), which might be exactly why there is so much flux in the party system at the moment. Once these forces resolve themselves, it is very possible minor parties will again become crowded out of Westminster elections.
Finally, a brief comment on why Duverger's Law continues to apply to the American system. As much as European believe that money explains everything that's different (or wrong) with politics in the United States, if that were the answer, then millionaires like Ross Perot could simply buy a third party organization and displace the other parties. We saw how that turned out.
I think a combination of factors make third party challenges difficult in the US. Duverger's Law is part of the story--we simply don't have alternative voting systems in most elections that allow third parties to compete with any great success. Add to the mix how the two main parties have made it nearly impossible for third parties to access the ballot, and one quickly realizes that the rules of the game perpetuate the dominance of the Democratic and Republican Parties. Finally, primaries--not a feature of politics in the United Kingdom--allow for grassroots forces and political issues that might be ignored by political elites to create an intra-party insurgence that in the UK might best be explored and initiated outside the main parties. One begins to see more support for Duverger's initial proposition after all. The rules of the game structure choice, and that's why--at the end of the day--all the love for alternative parties in the 2015 General Election may fade once the two main parties adjust to the new issues and political realities.
Which, frankly, would be nice because then I wouldn't have to change all my lecture notes....