By 1925, and partly influenced by the abstentionist tactics of Sinn Féin, the Scots National League had decided to contest elections, hoping to induce a majority of Scottish MPs to withdraw from the Westminster Parliament to convene an independent Scottish Parliament in Edinburgh. The SNL also established the Scots Independent newspaper in 1926 to further their aims.
From 1927 onwards, the SNL began to campaign for a Scottish national party. Together with its participation in the electoral process, this change made easier its liaison with the Scottish Home Rule Association, and its subsequent merger into the National Party of Scotland (NPS).
By the time of the formation of the NPS, the Scots National League had outgrown its London roots and become stronger in Scotland, largely due to the influence of Tom Gibson. Gibson had realised that nationalist politics needed to be connected to everyday issues in order to become popular. This strain of thought was prominent within the NPS and many former Scots National League members drifted from it due to their belief that the NPS was too moderate. This included Ruairidh Erskine himself, who drifted entirely from politics.
The SNL had a number of branches but its membership never exceeded 1000.
Further reading
Barberis, Peter, McHugh, John and Tyldesley, Mike, Encyclopedia of British and Irish Political Organizations, Bloomsbury, 2005
Brand, Jack, The National Movement in Scotland, Routledge and Kegan Paul, 1978
Richard J. Finlay, Independent and Free: Scottish Politics and the Origins of the Scottish National Party 1918-1945, John Donald Publishers, 1994