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 formation of the First Dáil's Irish Republic in 1919, Robbins held a position within 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 electoral district.