Post world war two until 1997 only had two parties winning almost all of the seats in Parliament. In that year the Liberal Democrats rose to 46 seats and have been over 50 seats in the next three elections. In 2010 this lead to a hung parliament, as they call it in the UK. This lead to the Conservative/Liberal Democrat coalition government. The 2015 election polls do not indicate this is likely to repeat itself.
The Parliament at Westminster has 650 MPs of which after the 2010 election 28 of them were not from one of the three main parties. 17 of the 28 are the Northern Irish MPs
Non Major Party MPs
6 Scottish Nationalist
3 Plaid Cymru
5 Sinn Fein
Other Northern Irish
8 Democratic Unionist Party
As long as all these parties together can not equal the number of seats the Liberal Democrats win they are effectively not an important factor in the formation of a government, but what we are looking at is a dramatic fall in the number of seats the Liberal Democrats are likely to win.
What various prediction sites are suggesting for the number of seats likely to be won:
- Conservatives 282 (278-286)
- Labour 272 (265-279)
- SNP 48 (40-55)
- Lib Dems 25 (22-28)
- DUP 8 (7-8)
- Sinn Fein 5
- Plaid Cymru 3 (2-4)
- UKIP 3 (1-5)
- SDLP 3
- Other 4
The exact numbers are not vitally important, it is the broad reality that the SNP will likely hold almost as many seats as all the other small parties that matters. As the Lib Dems were the only crucial factor for government formation in 2010, the SNP will be the ones in 2015.
325 MPs are needed for a majority, or 323 if one does not count Sinn Fein. What you can see from the numbers above is that only the SNP will likely hold enough seats to be a viable coalition partner for either major party. The problem is that neither major party is going to want to form a government with the SNP
The Conservatives are a very unionist party and a coalition with the SNP is off the table for that reason alone, The policies of the two parties are very much at odds with each other making coalition impossible on ideological grounds.
Labour would have trouble being in a coalition with the SNP because it would give the Conservatives a wedge issue to use in England to show Labour is not for the United Kingdom. Labour and the SNP would also have troubles working as a coalition because they are primary political adversaries in Holyrood.
Between the SNP, Plaid Cymru and Sinn Fein, nationalist parties wanting out of the UK are likely to hold 50 to 60 seats. For the SNP there is no upside to making the United Kingdom work because this would delay independence. The scale of what would have to be on the table in terms of more devolution would likely be more than the public in England would accept, not that this would be a problem for the SNP.
Canada could show the UK what may be ahead.
The Bloc Quebecois held a significant number of seats in the Canadian parliament from 1993 to 2011. With such a large block of seats in the hands of a party not wanting to see Canada function the path to a majority government was not easy for anyone. The Liberals barely managed a majority in 1997, they managed to luck out on how the vote split to win a number of close races. In 2008 when it was suggested that an Liberal/NDP colaition government would govern with the support of the Bloc, there was a huge backlash in the public to the idea of a government relying on the support of separatists.
Without the SNP how does one get to 323? If the Conservatives managed to get the Lib Dems, DUP and UKIP into one governing coalition, they would only be at 318 or so, five seats short. Though a coalition including both UKIP and Lib Dems is highly unlikely.
Even if both Labour and the Conservatives are at the high end of their estimates, they still do not have any clear path to majority. One or the other of them would have to break at least 300 seats.
This leaves one option for a coalition government that would have a working majority would be a Conservative/Labour one. This would be a more realistic government than one including the SNP.