Irish nationalists Sinn Fein have surged to the top of an opinion poll five days ahead of an election that looks set to be a major breakthrough for the former political wing of the Irish Republican Army.An Irish Times/ Ipsos MRBI poll published on Monday found support for left-wing Sinn Fein at 25%, making them a clear leader, with support for centre-right Fianna Fail at 23%. Support for governing Fine Gael was 20%.