Éamon de Valera new line. However, a vote to accept the Free State Constitution (contingent on the abolition of the Oath of Allegiance) narrowly failed. Soon afterward, de Valera resigned from Sinn Féin and seriously considered leaving politics. However, one of his colleagues, Seán Lemass, convinced de Valera to found a new republican party. In March 1926, with Lemass, Constance Markievicz and others, de Valera formed a new party, Fianna Fáil ("The Warriors of Destiny"), a party that was to dominate 20th-century Irish politics. While Sinn Féin still held to an abstentionist line, Fianna Fáil was dedicated to republicanising the Free State from
Éamon de Valera with the support of at least seven independents. The result was the First Inter-Party Government, with John A. Costello of Fine Gael as its compromise candidate for Taoiseach. Costello was duly nominated, consigning de Valera to opposition for the first time in 16 years. The following year, Costello declared Ireland as a republic, leaving partition as the most pressing political issue of the day. De Valera, now Leader of the Opposition, left the actual parliamentary practice of opposing the government to his deputy, Seán Lemass, and himself embarked on a world campaign to address the issue of partition. He visited