RN Collection: Mary Lou McDonald. Sinn Fein Vice President, Mary Lou Mc Donald, will be elected as the new leader and President of sinn Fein, to succeed Gerry Adams, in February 2018. End. 18/11/2017. Sinn Fein Ard Fheis.L to R Deputy Party leader Mary Lou McDonald and leader of Sinn Féin in the Northern Ireland Assembly Michelle O'Neill at the Sinn Fein Ard Fheis in the RDS In Dublin today. Photo:Leah Farrell/RollingNews.ie