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. 21/1/2017. Sinn Fein Irish unity. Pictured (L to R) President of Sinn Fein Gerry Adams with Deputy Leader Mary Lou McDonald in the Mansion House in Dublin today, at a debate on Irish unity.Photo:Leah Farrell/RollingNews.ie