When the First Dáil established the separatist Irish Republic in 1919, the younger Robbins worked in the Dáil government's Department of Finance. He was nominated as a Sinn Féin candidate in the Longford–Westmeath constituency at the 1921 general election.
Upon the establishment of the First Dáil's Irish Republic in 1919, Robbins joined the Dáil government's finance department. He was subsequently chosen by Sinn Féin as a candidate for the 1921 general election in the Longford–Westmeath constituency.