Election 2015: the battleground seats

1 The struggle for Scotland: Labour v SNP Ukip will win a lot of votes in 2015, but of even greater consequence for Westminster is the dramatic surge in support for the SNP, which has opened up a huge lead in the polls, putting every Scottish seat into contention. The most significant of the many battlegrounds will be the one between the SNP and Labour. Scotland has long been a stronghold for Labour, which holds 41 of its 59 seats. The Scottish result, and Labour’s options after polling day, will hinge on whether the SNP can overturn daunting majorities, and generations of Labour dominance, in places such as Glasgow and Dundee.

Examples: Glasgow Central, Dundee West, Kirkcaldy and Cowdenbeath, Paisley & Renfrewshire South

2 The coalition divorce: Lib Dem-Conservative marginals The seats where the coalition partners are pitted against each other will be crucial for both. The Conservatives are the main challenger in two-thirds of Liberal Democrat seats and polling suggests the Tories are doing better in these than in contests against Labour or the Scottish National party. These tend to be wealthier, suburban and rural seats in south-west England, where Liberal strength stretches back centuries, or south-east England, where they have consolidated opposition to the Conservatives. The Lib Dems’ chances will hinge on their ability to use local political machines and popular incumbents to hold on against the tide.

Examples: Eastleigh, Sutton and Cheam, St Ives, Torbay

3 The battle on the beaches: Ukip v Con (and Lab)

The challenge from surging Ukip support will be most directly felt in the emerging Ukip heartland along the English east coast. Ukip’s hopes for a big Westminster presence depend on its ability to break through in declining port and resort seats where large numbers of older, less well-off white voters cluster in large numbers. Most of Ukip’s strongest prospects come in Conservative held seats, but there are some Labour-Ukip battles to watch too.

Examples: Clacton, Thanet South, Great Yarmouth, Boston and Skegness, Great Grimsby, Hartlepool

4 The traditional swing seats: Lab-Con marginals The electoral dominance of Labour and the Conservatives is built on their large heartland territories. The Tories can rely on close to 200 “safe seats”, mostly in the arc of prosperous shire and commuter belt England surrounding London. Labour dominates a similar number of seats in industrial northern England and south Wales. General elections are usually decided in the smaller set of “swing seats”, where neither party dominates. These tend to be seats that contain a more diverse mix of electors – port seats such as Waveney, Suffolk, where dock workers and seaside retirees mingle; large market and university towns containing a full and representative social mix and similarly mixed seats on the suburban fringes of the big metropolitan areas. These seats will be critical in 2015, but they are becoming rarer. The results in 2010 left only 286 seats where the Conservatives and Labour took the top two positions – the lowest ever – and only 85 of these are marginals, fewer than one in six of the 650 seats up for election. The traditional Tory-Labour swing seat is becoming an endangered species.

Examples: Lincoln, Ipswich, Gloucester, Cardiff North, Wolverhampton South

5 The three- (and four-) cornered fights: the rise of the Greens The rise of Ukip and the Greens has multiplied the number of three- or even four-way contests. and local competition becomes highly unpredictable as votes flow in multiple directions. Ukip surges have complicated calculations in some Lab-Con marginals, where each party now has to worry about competition from two opponents and where the split in the vote becomes pivotal. For example, Labour would not normally have a chance in Thanet South, where Nigel Farage is standing, but an even split between the Conservatives and Ukip could provide it with a route through the middle. Farther up the Thames estuary in Thurrock, Labour losses to Ukip could provide the Conservatives with a way to retain an ultra-marginal they looked certain to lose. Ukip plays a similar wildcard role in Con-Lib Dem fights in south-west England. In Watford, Labour, the Lib Dems and the Conservatives are all in the running and in Bristol West and Norwich South strong Green votes complicate local contests.

Examples: Cannock Chase, Plymouth Moor View, Thurrock, Thanet South (Con-Lab-Ukip); Camborne and Redruth, St Austell and Newquay (Con-Lib Dem-Ukip); Watford, Cambridge (Con-Lab-Lib Dem); Bristol West (Lab-Lib Dem-Green); Norwich South (Lib Dem-Lab-Green-Con)

6 The battle for urban liberals:

Labour v Lib Dems (and Greens)

The Lib Dems won a number of classic “urban liberal” seats from Labour in the 2000s, winning over students and young professionals angry about university fees and the Iraq war. Such “left” Lib Dems have defected to Labour in droves since 2010, making these seats top Labour targets. Recently, however, the Greens have emerged as a tempting alternative for voters who feel Labour is not leftwing or socially liberal enough, throwing the results into doubt.

Examples: Manchester Withington, Hornsey and Wood Green, Bristol West, Brighton Pavilion