2012 has been a great year for Ukip; they've secured their best ever local election results, best ever by-election results and caused a whole new headache for the political establishment. Nigel Farage has been a regular guest and panellist on almost every mainstream political programme and has cemented his status as one of Britain's best known voices. Mainstream commentators and editorials have spent a lot of time (and ink) debating the reasons for Ukip's growth, with the main headlines screaming that following the Rotherham by-election they're on the verge of becoming Britain's third party.

While the recent by-election results have been impressive they also need to be seen in context. By elections are a time for protest, and in Rotherham Ukip came second with 21% of the vote, but the real story of the night was the turnout, which was a dismal 34%. When contextualising the vote it should also be remembered that the reason for the by-election was because of the extortionate expense-fiddling antics of the outgoing Labour MP, as well as the very particular timings of the local Ukip adoption scandal. Are we really to believe that all of Ukip's new voters are going to stay with them come 2015?

There is definitely, and often justifiably, a widespread sense of anger and disillusionment with Britain's political class, and Ukip's polling is a short term symptom of that. This is backed up by research from YouGov, who found that the surge in support for Ukip coincided with George Osborne's widely derided budget. However, in some ways the party is ill equipped for the new political limelight. David Cameron's charge that Ukip are "fruit cakes and loonies and closet racists" is remembered because there's an element of truth to it. The recent expulsion of Kent council candidate Geoffrey Clarke over his comments on people with downs syndrome show that there are still serious issues with candidate selection. It's a familiar problem and can also be seen in the outdated homophobic attitudes of their recent candidates for Croydon North and Oxford council. This is not to say all Ukip members and supporters are homophobic, but rather that they've either got issues with their vetting process or a poor base to choose from.

However, the main reasons they will never become Britain's third party are because of geography and the voting system. Geographically speaking, Ukip are a very limited party, there are huge chunks of the country where they have never kept a deposit let alone threatened an MP. I grew up in Scotland, where Ukip have never made a dent, and now I live in London, where Ukip has no representation. If we throw the Welsh Assembly and most of the big city councils into the picture and you can see a party that is too stretched and thin on the ground to mount a serious national campaign. There have definitely been local council success stories, but they're a long way off from making the necessary impact to replace the Liberal Democrats.

But then we come to Europe. Ukip's European success can't be dismissed lightly, but there's no reason to believe it can be repeated in a general election. In the 2009 European Elections they did extremely well, averaging about 15% across the country, but in 2010 they felt the impact of an increased turnout, bigger money and an election narrative that wasn't fixated on Europe and they were reduced to a mere 3.1%. This April, Ukip were polling at 9%, ahead of the Liberal Democrats, but ended up only winning a handful of seats and failing to reach the 5% requirement for the London Assembly. This suggests that Ukip's support is softer than that of the three main parties and more likely to fall away on election day. This point is particularly evident in their most recent polling. Opinium research put Ukip on 14% while YouGov put them on 8%, this may seem like a small difference but it's a change of 43%.

The reality is that much of this is not Ukip's fault. They neither have the budget, media coverage nor national base of the three main parties. They're also victims of the first past the post system, which ensures that there isn't a single seat anywhere in the country that they can expect to win. The polling suggests that the Liberal Democrats will suffer badly and that after the next general election Britain will recede back to adversarial two-party politics with little room for minority voices. Ukip will definitely play a role in the next election, with some analysts suggesting that it was Ukip who cost the Tories a majority in 2010. Can they do the same again in 2015? They will almost certainly be hot on the heels of a strong showing in 2014's European elections, and should they succeed in pressurising Cameron into announcing the in-or-out referendum that leading Tories and much of the wider public are calling for then they may have done something even more important than coming in third place.

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