Prior to 1967, the Hamilton parliamentary constituency was widely perceived to be an impregnable Labour party stronghold. As in many places in Labour's urban, working-class heartlands in the West of Scotland, it was said the Labour vote "is not counted here, it is weighed". This made Ewing's victory - on an unprecedented and gargantuan near-38% swing from Labour - all the more remarkable.
Until 1967, the SNP had struggled to make any significant, successful waves in national politics, remaining a largely small, fringe party. Although Robert McIntyre had become the SNP's first-ever MP after winning the nearby Motherwell constituency in a by-election in 1945, Ewing was not expected to win in Hamilton in 1967. In the 1966 UK General Election, the SNP had not even fielded a candidate in Hamilton. The SNP's leadership merely told Ewing to "try to come a good second in order to encourage the members". "As ever," Ewing later wrote, "I overdid it, and as a result my life changed for ever."
A by-election was called after the former Labour MP, Tom Fraser, resigned in order to take up a better-paid position as head of the North of Scotland Hydro-Electric Board. As his successor, Ewing held the seat until the 1970 UK General Election.
Today, Ewing's victory is recognised as both historic and iconic. It is seen as heralding the start of a new era in Scottish politics in which Scottish nationalism was now truly a force to be reckoned with and as the catalyst for the rise of the SNP from a minor party of protest to a mainstream party of government.
Ewing's first words to the crowd outside the count after her victory was declared - "Stop the World, Scotland wants to get on" - are among the most famous and most quoted ever to be uttered by a Scottish politician.