He stood as the SNP candidate for Member of Parliament for Argyll in 1970. On his second attempt, MacCormick was elected Member of Parliament for Argyll at the February 1974 general election, gaining the seat from the Conservatives.
In 1970, MacCormick ran as the SNP candidate for the Argyll parliamentary seat. He won the seat in 1974 after a second attempt, defeating the Conservative party.