Hung Parliament Battleground

This page first posted 13 December 2014

In post-war history, the UK has tended to have single-party governments which enjoy a majority in the House of Commons. When a minority government needed support from a smaller party it has always been the Liberal Democrats (Con/Lib Coalition government 2010-2015), and its Liberal Party predecessor (Lib-Lab pact, 1977-1978). However, the recent Scottish Independence referendum in September 2014 has transformed the landscape for coalition building. This article describes how the changes in Scotland affect the rest of the UK, and explores the new possibilities in the event of a hung parliament.

Scotland in recent years has returned a large bloc of Labour MPs. In 2010, Scottish Labour received 42% of the votes in Scotland and won 41 out of 59 seats. This group has traditionally formed a significant part of the parliamentary Labour party. The SNP, by contrast, received 20% of the votes and won only 6 seats. However, despite losing the referendum vote, the SNP has been energised by the independence campaign and its party membership has soared. It has also increased its predicted Westminster voting intention level to 43% (as at November 2014), whilst Labour has fallen to 27%. This would reverse the previous Scottish election result, and could see the Nationalists win about 47 seats, with Labour reduced to 11 seats. This change would have two major effects. Firstly, the loss of thirty seats makes it harder for Labour to have an overall majority at Westminster. And secondly it makes it likely that the SNP would be the third largest party in the House of Commons, which completely transforms the possibilities for coalitions and pacts.

Electoral Calculus has run a large number of scenarios to explore this new world of hung parliament possibilities, and to estimate their probabilities. The overall complexity is best shown with the following graphic:

UK Hung Parliament Battleground

Source: Electoral Calculus

Hung Parliament Battleground

Currently there is about a 50% chance of a hung parliament in 2015, and this graphic shows the battleground area focusing on the hung parliament scenarios. The growth of SNP support in Scotland creates a genuine four-party system at Westminster with a range of possible coalition permutations. Conservative support is given by the horizontal axis, and Labour support by the vertical axis. The current support position (Con 30.7%, Lab 33.2% at December 2014) is shown by the circular blue marker inside the "Lab choice of Lib/Nat" zone, where Labour can choose its coalition partner.

The map only shows movement for the Conservative, Labour and Liberal Democrat parties. It assumes the votes for other parties, including UKIP and the SNP, are fixed at current support levels. UKIP are not currently to predicted to win many seats, so they are not yet a factor in coalition permutations. Since other parties have 28% support nationally, the map is missing the top-right corner where the Conservative plus Labour total would be more than 72%.

Coalition possibilities

Previously there were only a limited number of two-party coalition possibilities because the only likely partner was the Liberal Democrats. So the two-party options were limited to a Con/Lib coalition and a Lab/Lib coalition, with an interesting sub-case being when both options were possible at the same time, and the Liberal Democrats might effectively be able to choose between the two major parties to select which forms the government. Technically that gives six possibilities (Labour majority, Lab/Lib coalition, Lib choice of Con/Lab, no overall control, Con/Lib coalition, and Conservative majority).

But the arrival of a large bloc of SNP MPs would increase the number of possible two-party permutations to twelve. Here is the description of these possibilities for coalition government, going clockwise from top-left:

  1. Labour majority: if Labour gets at least 326 seats it has a majority in the House of Commons, and does not require the assistance of any other party to govern. Very small majorities can be problematic, but this scenario is the ideal result for a large party.
  2. Labour choice of Lib/Nat: if Labour is only a few seats short of 326, then they could form an alliance with either the Liberal Democrats or the SNP. This would give Ed Miliband a fairly strong negotiating position, but he might ultimately favour the Lib Dems.
  3. Labour/Nationalist coalition: In this area, the only possible two-party coalition is Labour and the Nationalists. This would give the SNP considerable influence, though some three-party options might also be available to Labour.
  4. Nationalist choice of Con/Lab: the Nationalists have so many seats that they can form a viable coalition with either the Conservative or Labour parties. That would give them very considerable influence over the UK government. The SNP have previously declared that they would not form an alliance with the Conservatives. If they hold to this position, then that would decrease their negotiating power in this scenario.
  5. Conservative/Nationalist coalition: this possibility would throw up problems since the only workable two-party deal would be between the Conservatives and the Nationalists. As the SNP have currently ruled it out, there might be pressure on them to give ground or an early second general election.
  6. Conservative majority: where the Conservatives get at least 326 seats and do not require a smaller party ally to govern. This has not happened since John Major won in 1992.
  7. Conservative choice of Lib/Nat: if the Conservatives are just below 326 seats, then they could make an alliance with either the Liberal Democrats or the Nationalists. David Cameron might be likely to prefer his existing coalition partners over the SNP, so this option may be similar to its sequel.
  8. Conservative/Liberal coalition: where the only viable two-party coalition is between the Conservatives and the Liberal Democrats. This was the outcome of the 2010 general election, but is less likely to happen in 2015 because of the decline in Lib Dem support.
  9. Liberal Democrat choice of Conservative/Labour: if the Liberal Democrats increase their support and win many seats, then they could be the powerbrokers with the choice of whether to keep David Cameron in Downing Street or switch to Ed Miliband. Convention suggests that Nick Clegg might favour whichever big party has more seats, but there is no rule to do that.
  10. Liberal majority: if the Liberal Democrats get 326 seats they can govern on their own for the first time since Henry Campbell-Bannerman in 1906. This is very unlikely, and this area is not shown on the graphic map.
  11. Labour/Liberal coalition: if the only possible two-party coalition is between Labour and the Liberal Democrats. Currently this is not a likely scenario.
  12. No overall control: in this central area there are no two-party combinations which have 326 seats. In this case, there would either have to be a multi-party coalition (see below) or fresh elections.

The table below shows possible examples of each of the twelve scenarios. Note that the examples of the first seven types can be found without even changing the current Liberal Democrat support level and only by varying Labour support within the narrow range between 28.6% and 35.0%.

1. Labour majority
Labour majority of 22 % Vote
2273362104719Pred seats
2. Lab choice of Lib/Nat
Labour need six seats - could be LibDem, SNP, or DUP
30.633. % Vote
2433191905019Pred seats
3. Lab/Nat coalition
Labour need 29 seats - only SNP have enough % Vote
2672971804919Pred seats
4. Nat choice of Con/Lab
Labour need 40 seats, Conservatives need 46 seats. SNP have enough for either % Vote
2802861604919Pred seats
5. Con/Nat coalition
Conservatives need 24 - only SNP have enough
34.429. % Vote
3022671404819Pred seats
6. Conservative majority
Conservative majority of 30 % Vote
3402311104919Pred seats
7. Con choice of Lib/Nat
Conservatives need 8 seats - could be LibDem or SNP
35.428. % Vote
3182531204819Pred seats
8. Con/Lib coalition
Conservatives need 64 seats - only LibDems have enough % Vote
2622149705720Pred seats
9. Lib choice of Con/Lab
Labour need 85 seats, Conservatives need 90 seats. LibDems have enough for either
25.622.623.917.243.5 % Vote
2362419705620Pred seats
10. LibDem majority
Lib Dem majority of 28 % Vote
8215833905021Pred seats
11. Lab/Lib coalition
Labour need 71 seats - only LibDems have enough
24.623.623.917.243.5 % Vote
21825510205520Pred seats
12. No overall control
Labour need 59 seats. Conservatives need 66 seats. No other single party has enough. % Vote
2602674805520Pred seats

The current probabilities of these scenarios can be seen on the home page. As at December 2014, they were:

Labour majority (1)
Lab/Nat coalition (3)
Lab choice of Lib/Nat (2)
Con/Nat coalition (5)
Conservative majority (6)
Nat choice of Con/Lab (4)
Con choice of Lib/Nat (7)
No overall control (12)

So the probability of a good outcome for Labour (options 1, 2, 3, 4, 11) where Ed Miliband is Prime Minister is 77%. The probability of a good outcome for the Conservatives (options 6, 7, 8) with David Cameron staying in Downing Street is only 12%. A good outcome for the SNP (options 3, 4, 5) has them controlling the balance of power, with a probability of 33%. A good outcome for the Liberal Democrats (options 2, 7, 8, 9, 10, 11) has probability of 16%.

These probabilities will change as the election approaches.

Other possibilities

Even the list of twelve scenarios above is not exhaustive and other outcomes can happen. In brief, they are:

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