The association was sufficiently neutral to act as the honest broker between the various nationalist organisations which would merge to form the National Party of Scotland (NPS) in April 1928.
In consequence, MacCormick initiated a campaign to redefine the policy of the NPS, to make it more moderate and to tone down demands for independence.
He considered the basic problem to be that, although many people in Scotland favoured home rule, they were not, on the whole, willing to put the issue above conventional party loyalties.
[3][4] As a leading figure in the SNP, MacCormick came under increasing attack from the rank and file members for his failure to maintain party structure and organisation.
[3] He endeavoured to present an acceptable face of Scottish nationalism, and did much to reverse the party's official anti-conscription policy following the outbreak of the Second World War.
[1] This covenant was hugely successful in securing support from across the political spectrum, as well as in capturing the Scottish public's imagination (over 2 million signed a petition demanding the convocation of an Assembly).
[1][3] His failure discredited claims as to the popularity of home rule, and further served to reinforce notions that the Scottish Convention was an anti-Labour organisation.
[7] This association with GUSNA also saw the formation of a political friendship with a then young law student at Glasgow University, Ian Hamilton, who had run his campaign to be elected rector.
His last attempt to enter parliament came at the 1959 General Election, when he stood for the Liberal Party at Roxburgh, Selkirk and Peebles, again finishing second.
Their second son, Neil (1941–2009) was regius professor of Public Law and Vice-Principal of the University of Edinburgh, and served as an SNP Member of the European Parliament from 1999 to 2004.