The Ulster effect
The electoral map that most of the broadcasters use misses off Northern Ireland entirely. But if the election is as close as people expect, then those 18 seats across the Irish Sea could become vital. The first thing to note is that Sinn Fein remains committed to its policy of not taking its seats at Westminster. So every Sinn Fein MP elected reduces the number that a party needs to have an effective majority in the Commons. Iris Robinson, expenses and the rise of Traditional Unionist Voice have all rather dented the DUP, the largest party in Northern Ireland at the last election. But it should still send back a fair few MPs.