In October 1967 John Mackintosh, the Labour MP for Berwick and East Lothian and a Professor of Politics at Strathclyde University, reflected on the rise in popular support for the SNP that had taken place since the start of the decade. Published in the Political Quarterly, Mackintosh’s assessment arrived a month before the SNP’s landmark electoral victory at the Hamilton by-election, when Winnie Ewing famously overturned what had been the largest Labour majority in Scotland. If Ewing’s triumph has come to be remembered as a seminal moment in post-war Scottish politics, one which signalled the onset of a new period in which the constitutional question would become increasingly unavoidable, Mackintosh’s prescient consideration of the SNP’s appeal offers a reminder that contemporaries were becoming conscious of the growing political significance of the SNP even before Hamilton. Certainly, by the mid-1960s it was evident that the SNP could run credible, if not yet successful, by-election campaigns. Further, as party membership rose, from around 2,000 in 1962 to perhaps 42,000 by late 1966, it became financially and logistically feasible for the SNP to contest general elections on a broader basis. At the 1955 general election there were just two SNP candidates; four years later the party was still only able to contest five constituencies. By the time of the 1966 general election, there were SNP candidates in twenty-three seats, and the party received five per cent of the Scottish vote. While not yet a serious political force, by the second half of the 1960s the SNP clearly enjoyed a support that was larger and more secure than it had been at any time since the party’s foundation. That the new, still minor, influence enjoyed by the SNP might have wider political consequences had been apparent since the March 1967 Glasgow Pollok by-election, when the party’s candidate, George Leslie, had polled twenty-eight per cent of the vote, a performance that enabled the Conservatives to record a rare gain from Labour in Scotland.

For Mackintosh, the paradox that required explanation was that the rise in support for the SNP had occurred during a period in which Scotland had, in social and economic terms, become ever more like the rest of Britain.