A key reason for Thatcher’s removal by her parliamentary colleagues had been the belief that she would lead the Conservatives to election defeat. Against expectations, Major managed to win a 21 seat majority in the 1992 election, gained the most votes any leader has for any party before or since and won a personal majority of over 36,000 votes in his Huntingdon constituency. What could possibly go wrong?
While serving briefly as Chancellor of the Exchequer before becoming premier, Major had persuaded Thatcher to allow the Pound to join the Exchange Rate Mechanism (ERM) – the forerunner of the euro. In September 1992, just five months after the election victory, the Pound was forced out of the ERM. In reaction, the Conservative Party became more euro-sceptic and less-disciplined, its economic policy had to be re-written and Major's reputation sank. His party began to crumble at the edges.
Despite vigorous and visible attempts to control his party (including Major’s resorting to resigning and re-contesting the leadership) the Conservative majority in Parliament leaked away, leaving Major running a minority government as he limped towards defeat in 1997.
Four Conservative MPs died and their seats were won by Liberal Democrats in by-elections (Newbury, Christchurch, Eastleigh and Littleborough & Saddleworth). Four others died and their seats were won by other parties (Dudley West, Staffordshire South East and Wirral South by Labour, Perth & Kinross by the SNP).
Two Conservative MPs defected to the Liberal Democrats (Emma Nicholson and Peter Thurnham). Alan Howarth defected from the Conservatives to Labour and George Gardiner defected to the Referendum Party.
If the four defectors had remained in the party, the Conservatives would still have held a fragile majority in parliament. Individual political defections usually only attract fleeting attention, but their cumulative effect can be game-changing. Defections are not just storms of protest, but can be indicators of political climate change.
The Liberals had been the party most prone to losing defectors in the first half of the 20th century, then it was Labour’s turn with the SDP split in the 1980s, but since the 1990s the Conservatives have been the party most vulnerable to defections.