So it’s official: Nigel Farage will contest South Thanet at the 2015 general election. This is not exactly unexpected – there has been a lot of quite detailed analysis of UKIP’s electoral prospects in the build-up to and aftermath of the European elections by the likes of Rob Ford, Matthew Goodwin and Lord Ashcroft, and all of it paints South Thanet as exactly the sort of seat UKIP will – or at least can – perform strongly in.

It is almost a certainty that Farage will handsomely surpass his disappointing 2010 performance, when he ran against John Bercow in Buckingham and was beaten into third place by the founder of the Pro-Euro Conservative Party. Personally, I still think he might have missed his shot by ducking the Eastleigh by-election, which his star power would surely have carried for the party. It will be much harder for the leader of a minor party to maintain a media profile in the heat of a national, who-will-run-the-country election.

But let’s assume he wins. UKIP get their breakthrough and their first MP. It will definitely be a watershed moment, of a sort. As one BBC presenter said of the SNP as they lost ten of their eleven seats in the 1979 election, there is a big difference between a party with Westminster representation and a party without it.

The will be a short-term impact, too. Farage, and any other UKIP MPs who might make it over the line, will go and sit with the Democratic Unionists in the very-right-wing, pro-Union section of the “Others”, and from there they can open up a new front in their guerrilla war on the ‘Establishment’. It will also be marginally harder for the Conservatives to put together a government committed to an In/Out referendum.

But the question nagging me is – where does UKIP go from there? There are two quite distinct paths open to UKIP if it manages to win a Westminster toehold, each of which appeals to different sections of UKIP’s support and leadership.

The first is attempting to build itself up into a permanent, national party. By any reckoning this will be long, slow and hard work – European election results have not translated well into general election performance since the former switched to PR, according to research by British Future. But it is definitely possible. Contrary to popular perception, UKIP actually has the most working-class support base since Michael Foot led Labour. It appeals to voters – older, male, working-class, socially conservative – who have been left behind by the political consensus since the Eighties.

Not only do these voters offer UKIP the potential to break through in Labour areas – according to Dr Goodwin by 2020 they could be bringing into contention Labour seats which have been safe for generations – but by capitalising on the collapse of the Liberal Democrats in the north they could become the next anti-Labour party in the great northern cities. That UKIP has started mimicking the Lib Dems and pouring time and effort into its local government operation is evidence that the party is wise to this opportunity.

Factor in the very real prospect of elected representation in all three devolved chambers, and it is quite clear that with a couple of decades of hard work UKIP could mirror the rise of the Liberal Democrats and become this country’s fourth – or even third – party.

The other path is what The Week termed a ‘reverse takeover’: use the party as a vehicle for shifting the political centre in a given direction, and then dispose of it. Nigel Farage likes to describe the SDP as the most influential political party of the late 20th Century because, to paraphrase, we ended up with three of them. The SDP, UKIP supporters should note, is conspicuous today by its non-existence.

On this model, UKIP brings sufficient pressure to bear to move the Conservatives where Farage wants them, and then reunites the right – on Farage’s terms.

It’s easy to see why this attracts Farage – and it isn’t just because he probably doesn’t have two decades of frontline politics left in him. Farage, like a lot of UKIP activists but crucially unlike most of the party’s potential support, is a committed Thatcherite. Apart from getting out of Europe, what he’d really like is the ‘proper’ Conservative Party back. Moreover, he is deeply opposed in principle to the sort of policies that would maximise his party’s potential vote, especially on economic matters: patriotic protectionism, industrial policy, and so on.

Yet the more UKIP attempts to move away from being perceived as ‘single issue’, the more it attracts people who don’t view it as a vehicle for leaving the EU. As Daniel Hannan has noted, the more time and effort people spend pounding the streets, running for councils and assemblies, and serving in elected office, the more people are getting attached to UKIP as a party.

This probably won’t matter so long as Farage remains leader, and of course it is impossible to know what impact an In/Out referendum could have on the UKIP phenomenon, whatever the outcome. But such a referendum will bring these questions to a head: the party will be forced to decide, and articulate, whether or not it has a purpose beyond the EU and, if so, what that purpose is.

It seems likely that whoever succeeds Farage as leader will be drawn from the new school of UKIP politicians, who are more attached to the party and better prepared to make the leftward adjustments of course required to align the party best with the economic inclinations of its potential voters. In which case the party could well become a permanent fixture of British politics – in a form that Nigel Farage never intended, and probably would not like at all.