The 1966 United Kingdom general election on 31 March 1966 was easily won by sitting Labour Prime Minister Harold Wilson. Wilson's decision to call an election turned on the fact that his government, elected a mere 17 months previously in 1964, had an unworkably small majority of only 4 MPs. The Labour government was returned with a much larger majority of 96.
Prior to the general election, in 1965, Labour had performed poorly in local elections, and lost a by-election, cutting their majority to just 2. Labour ran its campaign with the slogan "You know Labour government works".
The Conservatives had not really had time to prepare their campaign, although it was more professional than previously. There had been little time for Heath to become well known among the British public. For the Liberals, money was an issue: two elections in the space of just two years had left the party in a tight financial position.
Research Services : 3% swing to Labour (forecast majority of 101)
National Opinion Polls : 3.5% swing to Labour (forecast majority of 115)
Gallup : 4.5% swing to Labour (forecast majority of 150)
Express (known as Harris): 7.5% swing to Labour (forecast majority of in excess of 255)
The 5,117 votes polled for the "Others" in Nelson and Colne were all polled for Patrick Downey, uncle of Lesley Ann Downey who had been murdered by the Moors Murderers. Downey advocated the return of hanging.
^The BBC lists this result as 363 seats, which would give a majority of 96, due to the Speaker's seat being listed as "other", although the BBC tends to include the Speaker in the party totals. 364 seats would naturally result in a majority of 98.