The end of a three-party UK?

General election campaigning is getting under way in earnest, with battle lines being drawn along familiar ground. The Conservatives are highlighting their stewardship of the economy, Labour is focusing on the NHS, the Liberal Democrats are placing themselves in the middle between the big two, and the SNP are pitching for better representation of Scotland at Westminster.

Pitches for tactical votes are familiar too, with SNP deputy leader Stewart Hosie MP saying “by electing SNP MPs, the people of Scotland can vote to get rid of the Tories, and have a powerful voice to protect and promote Scottish interests,” while Scottish Labour leader Jim Murphy says: “Scotland can protest against the Tories by voting for any party, but only Labour can replace them.”

But while the script might look familiar, this is no ordinary General Election. As Holyrood revealed this week, experts like Professor Richard Rose predict a result with no clear winner. We are no longer looking at a three-party system across the UK

The last election in 2010 was unlike any which had preceded it. Constituency boundaries had shifted, polls suggested the Liberal Democrats might come of age and herald a three-party system, and for the first time we witnessed television debates between prime ministerial hopefuls in the style of the American presidential prime-time showstoppers.

What Britain got at Westminster, of course, was its first coalition government since the early 1940s, which went on to secure its future by introducing five-year fixed-term parliaments. But if the 2010 election was hard to predict, its sequel is giving pollsters a proverbial migraine.

Having received nearly a million votes in 2010 - more than the Greens, SNP and Plaid Cymru put together - the UK Independence Party (UKIP) hopes this time to turn support into seats. Those other parties, too, may have greater influence than before.

And while the structure of televised debates is up to individual broadcasters, the tête-à-tête about who should be included reveals one thing: the UK political map is fundamentally changing.

“Constituency competition between five or six parties is the new norm. This increases the importance of shifts in votes between third-force parties and the Conservatives and Labour,” writes Professor Rose. Opinion polls “cannot be reliably used to predict the number of seats each party wins,” he says.

According to seat-by-seat polling by Lord Ashcroft, what were once safe Labour and Liberal Democrat seats in Scotland are under threat from the SNP.

Rose highlights in his report no British government has won an absolute majority of the vote since 1935, and now with at least five parties contesting most constituencies, “the party coming second there is often not the official opposition party in the House of Commons”.

Alan Convery, a lecturer in politics at the University of Edinburgh who specialises in the political parties for the Centre on Constitutional Change, says the two-party system has been under strain for a long time. “You have a party system that’s become increasingly multi-party. If you draw a line graph from the 1950s there’s about 80 per cent votes for the two main parties in the 1950s and it just goes down every single election,” he says.

 “Parties will be very well aware of Nick Clegg’s experience in terms of tuition fees"

The Liberal Party, then the Liberal/SDP alliance and now the Liberal Democrats, have seen their vote share generally increase in that time (see graph). However the 2010 result, when they finally took their place in government, may have heralded more than a three-party system.

The Liberal Democrats, Convery points out, “are no longer the go-to protest party, they’re now in government,” which has benefitted the others. “There’s two wings of the party – the social democratic wing and the small-l liberal wing, and what happened was you had a lot of party members and voters who were on the social democratic wing, but the leadership of the party were clearly small-l liberals. I think to govern is to choose, and they chose. It was always going to be a problem,” says Convery.

With the Liberal Democrats now part of the establishment, polls have suggested around a quarter of voters in the UK now intend to vote for parties outwith the big three, leaving constituencies across Britain becoming very difficult to predict.

Even if the polls narrow, the SNP hopes to increase its representation at Westminster from six MPs. Rose predicts it will get 45. However, Convery doesn’t see them or any other smaller party entering into a formal coalition. “Parties will be very well aware of Nick Clegg’s experience in terms of tuition fees, and not making hostages to fortune in that sense, also, what is acceptable to their own party, what is in their long-term interest? You need to see what is possible and also decide is the price of being in government too high?”

Both the Greens and UKIP have indicated they wouldn’t want ministerial posts. “Douglas Carswell [was] saying ‘we want the influence not the ministerial cars’, which is an interesting formulation,” says Convery.