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30 March 2015, 08:21 | Updated: 20 April 2015, 08:36
The general election campaign is well underway, as voters prepare to go to the polls in 650 seats across the UK.
But the outcome will be determined by the results in just a cluster of constituencies.
Most seats never change hands in national polls so the fight is focused on a small number of marginal battlegrounds that have previously mainly flipped between Labour and the Conservatives.
But the rise of the smaller parties has muddied the waters and left pollsters unable to predict the likely outcome on May 7.
Labour's biggest threat is north of the border with predictions that the party faces obliteration in Scotland come polling day following the rise of the SNP.
Pollsters have estimated that Nicola Sturgeon's party could all but wipe out Labour's Scottish power base and previously safe seats are now wide open races.
The SNP will be keen to claim high-profile political scalps with Scottish Labour leader Jim Murphy's East Renfrewshire constituency, won with a 10,420 majority, now vulnerable. Margaret Curran's seat in Glasgow East, won with an 11,840 majority, will also be firmly in its sights.
Labour has an "entirely offensive'' national campaign to win over 106 seats it does not currently hold - with four out of five currently held by the Conservatives. If the party succeeded in taking the seats they would be winning back 88 of those lost in 2010 and 15 from 2005 along with three others.
Warwickshire North, Hendon, Cardiff North, Sherwood, Norwich South and Stockton South are at the top of its hit list. It would need to take Norwich North from the Conservatives on an even nationwide swing to win the election.
The target list also includes Thurrock, traditionally a straight fight between Labour and the Conservatives and on course to return to the Opposition until the rise of Ukip.
Taken by the Tories by just 92 votes in 2010, it was Ed Miliband's number two target and one of his former aides, Polly Billington, was chosen as the candidate.
Now, it is in Ukip's crosshairs and is set to become one of the focal points of the campaign as the parties slug it out in a three way battle.
Matthew Goodwin, associate professor at the University of Nottingham, said Ukip is likely to affect the Conservative vote in up to 69 seats and Labour's support in up to 59.
He pointed to Thanet South, where Mr Farage is standing, Clacton and Rochester & Strood - where it currently has MPs - Thurrock and Great Grimsby, as key seats the party will be focusing on. Boston & Skegness will also be a key battle for the party.
"Most analysts are predicting Ukip will win between three and six seats but the indirect impact they will have is far wider,'' he said.
The Conservatives are said to be adopting a 40/40 campaign strategy that will see them targeting 40 seats they do not currently hold and 40 where they have small majorities.
Among the constituencies they will focus on are Hampstead & Kilburn, where Labour's Glenda Jackson is standing down, Bolton West, Solihull, Southampton Itchen, Mid Dorset & North Poole, and Wirral South.
The Tories are also gunning for shadow chancellor Ed Balls, who won his Morley & Outwood seat with a majority of 1,101. Claiming Newcastle-under-Lyme on an even nationwide swing would secure them victory.
Coalition has not been kind to the Liberal Democrats with the party's popularity plummeting to as low as six points in some polls and predictions it will lose around half of its seat.
The party is likely to put its efforts into shoring up support in its South-West heartlands, where the fight is against its Conservative coalition partners. In seats where its biggest threat is from Labour the ``game is up'' according to academics.
Although leader Nick Clegg's Sheffield Hallam seat is one of the safest the party holds, with a majority of 15,284, volatile polling suggests it could be vulnerable to a Labour win.
Chris Hanretty, reader in politics at the University of East Anglia and one of the contributors to ElectionForecast.co.uk, said: "We expect the Liberal Democrats to win 24 or 25 seats. They are going to try and stem the flow in seats where they are facing a Conservative challenger. Where they face Labour the game is up.''
He added: "I think Ukip will have its best results to the east of London in the estuary towns. Its long-term strategy may be to win seats in the north but short term it is not desirable.''
Mr Hanretty said the election forecast model the team uses is conservative in its predictions but still has the SNP on course to win up to 45 seats.
"A lot of the seats are seats you would not normally consider as battlegrounds but Jim Murphy and Edinburgh South will be ones to watch.''
But he added: "In the run up to the election we expect the parties that have been doing better in the polls, such as Ukip and the SNP, to fall back a little and the Conservatives and Labour to increase a little.''