Wolfe stood as SNP parliamentary candidate for West Lothian at the 1964, 1966, 1970, both elections in 1974, and 1979 general elections. In June 1969, at the SNP Annual National Conference in Oban, Wolfe was elected as chairman (leader) of the SNP, defeating the incumbent leader, Arthur Donaldson, by 544 votes to 238. Having swung his support behind the ‘It's Scotland's oil’ campaign that changed the party's fortunes, he associated the SNP with the trade union campaigns against shipyard and other industrial closures and asserted its role as a radical participant in Scottish politics. Wolfe was instrumental in identifying publicly the social democratic, left-of-centre credentials of the SNP. It was during Wolfe's period as leader that the party had considerable electoral success in elections to the Westminster parliament, winning 30% of the vote in Scotland and 11 of the 71 Scottish seats in the October 1974 General Election, though Wolfe failed to win a seat of his own in West Lothian in the two general elections of that year, despite gaining an increased share of the vote. His exclusion from the powerful new group of SNP MPs caused some difficulties for his leadership of the party. However, following a difficult period which saw the passing of the Scotland Act 1978, a number of internal divisions in the SNP and the failure of the party to win in a series of by-elections, in 1978 Wolfe announced his intention to stand down as leader after almost ten tumultuous years in office. The resultant loss of influence led to his being sidelined as the SNP moved into the 1979 general election campaign, and a disastrous performance in which the SNP only managed to retain 2 of their 11 MPs. Wolfe was succeeded by Gordon Wilson at the SNP Annual National Conference in September 1979. In 1979, Wolfe encouraged a band of left-wingers in the SNP, known as the 79 Group, annoying those on the fundamentalist wing. Although he was elected as president of the SNP in 1980, succeeding Robert McIntyre, Wolfe's term of office ended in June 1982, following an intervention by him in advance of the proposed visit of Pope John Paul II to Scotland, causing serious controversy by claiming the Pope represented an "alien culture". In a January 1982 letter to the Church of Scotland magazine, Life and Work, Wolfe attacked the appointment of a papal nuncio to the United Kingdom.