It would be indefinitely wiser to say that this is a reason why, and with some exploration they can be identified. The five years in between the 1992 general election and the record breaking landslide victory for labour in 1997 saw some terrible economic disasters happen to the country, what with the forced withdrawal from the Exchange Rate Mechanism (E.R.M) and the events surrounding “Black Wednesday” which saw the government’s inflation blocker being revoked and huge loss of value against other various European and global currencies. This was one of the most memorable failures of post-war British economic policy. It was the defining lead balloon of John Major's government and was a huge boost to Euro-scepticism. Policy-makers still bear the scars from that day - when speculators sold the pound, detaching it from its link to the deutschmark. The Exchange Rate Mechanism (ERM) had been the centre-piece of British economic policy - tie the pound to the deutschmark, it was said and you will get a German-style economy, with stability and low inflation. The removal from this and the fact that the countries economy was already in recession certainly suggests that at the next election the voters would rid them of what seemed like a bunch of incompetents. Furthermore when we look at more modern times of election we see the voters, are becoming a group who are less partisan. They no longer hold stable long term feelings of positive attachment to one of the main parties. This party identification developed through socialization or social learning in the home, but alongside the decline in partisanship was the decline in class voting. The social characteristics used to show a much more developed correlation between social class, such as occupation and lifestyle. The working class was made up of manual workers and they tended to vote for the Labour Party. The non-manual workers made up the middle class and there tendencies lay towards the Conservative party. As the party’s were looking to broaden their spectrum of support it could no longer be argued that a party represented the characteristics of a class grouping anymore, so a move away from this type of voting also is a factor. Issue voting is a key reason which can be considered in the outcome of a general election, it ever-increasing in its popularity, its is defined as being the deciding by people on how to vote by comparing the policies put forward by political parties on the major issues of the day. This assumes that the voter perceives differences between the parties and vote for the one closest to their own position.
We are seeing in times of recent elections, the “Americanization” of the campaign and saturation coverage given to the party leaders focusing on their personalities. It is unclear what party leaders have as an effect on the overall outcome but it thought to be of some significance and could lead to the change in winner if the election is a close run race. Another factor for consideration is Ethnicity, although turn out among black voters is low, an overwhelming number of ethnic minorities support Labour, this is thought to be about 80%. With the ethnic proportion growing in Britain perhaps this factor we will see develop more clearly over the coming general elections. Structural factors such as gender and age can be blamed for the change in the outcome of an election too, the post war period saw the Conservative most popular with women although in the last two elections, Labour have made significant gains as with the age group.
In conclusion, it is my belief that when trying to decipher the reasons why an election resulted in the way it did. The primary, secondary and subsidiary reasons are almost unfathomable, when looking at general elections a whole rather than a specific study on one particular one this is due to all the many factors listed in this answer as well as the volatility and unpredictability of governments and voting.