‘I have been asked repeatedly to form a political party; I have been asked repeatedly to stand as a candidate; I have so far refrained from doing so for various reasons.’ A month after Seán MacBride unblushingly declared his disinterest in party politics in a national newspaper, Clann na Poblachta was launched in Wynn's Hotel on 6 July 1946. The history of the party, including its part in the first inter-party government, has been well served in current historiography, and a brief survey of its principal moments will suffice here. While several authors have noted Clann na Poblachta's development from similarly named previous incarnations of the republican body politic, none have interrogated the crucial difference with the 1946 version: the abandonment of abstention as a political platform. MacBride was elected in the Dublin County by-election of October 1947, topping the poll on the basis of transfers from the Labour and Fine Gael candidates. In the general election of the following February, Clann na Poblachta won ten seats and entered government in Ireland's first coalition; MacBride took the seat of External Affairs and appointed his junior colleague Noël Browne to the Health portfolio.

The government's performance, as it staggered from one crisis to the next, was highly criticised; even the republican high point, the declaration of the Republic of Ireland, was mismanaged and anti-climactic. MacBride's own performance – as party leader and as Minister for External Affairs – has also drawn criticism. As minister, he courted early success, particularly in securing Ireland's place in developing European integration projects, but encountered significant failures in other key areas. The bungling of the Marshall Aid negotiations and the question of Irish entry to NATO were two of the most immediately obvious miscalculations; MacBride's obsession with partition was another. Partly attributable to the need to compete with de Valera's anti-partition world tour after his exit from government in 1948, MacBride's insistence on a ‘sore thumb’ policy with regard to partition did much to negate the value of Irish participation in European and international organisations, at a time when her isolation from the current of world affairs had been sharply wrought.