If the rise of the UKIP wasn’t enough of a shock to the system, consider the following possibility: that the ascent of Farage is only an intermediate stage in a much wider realignment of British politics.

The evidence is mounting up:

Firstly, the failure of the Lib Dems to recover in the polls – if anything, the party’s ratings are still edging down, with at least two-thirds of their 2010 support looking permanently lost to them.

Secondly, the rise of the Green Party. It may be premature to talk of five party politics, but the Greens are now regularly matching the Lib Dems in the polls and have three times as many MEPs (i.e. three MEPs). If the Greens are really lucky, their leader will be denied a place in the TV debates for the general election next year – thereby handing the party a heap of sympathy votes while saving the nation the bother of having to find out who Natalie Bennett is.

Thirdly, the decay of Scottish Labour. The SNP may have lost the war (for independence), but they’re winning the peace. Johann Lamont (Scottish Labour leader until last week) has done more to redefine Scottish politics in her departure than she ever did while in the job. Unless the party picks Jim Murphy to replace her, then Labour’s heartland could be under threat.

And this is just what’s happened so far. We’ve still got the impact of further UKIP victories, devo max for Scotland and next year’s general election to come.

The next Parliament could see the failing brakes on political realignment – i.e. first past the post, incomplete devolution and the institutional grip of the big two parties – give way altogether. If they do, there’ll be nothing to stop the emergence of a new system composed of a larger number of smaller political parties.

Last year, Tim Montgomerie imagined what this might look like in a column for The Times (non subscribers can view the accompanying graphic here).

In place of UKIP and the Conservatives, Tim imagines two new parties – the ‘Freedom Party’ and the ‘Nationals’. The former would be very eurosceptic and broadly libertarian in nature, the latter more moderately eurosceptic and ‘one nation’ in its values.

The Freedom/National split makes more sense than either the unhappy coalition-within-a-coalition that is today’s Conservative Party or the ideological mess that UKIP has become. However, I’m less sure about the other two parties in Tim’s scheme – i.e. the ‘Liberals’ (which he HAS encompassing a full range of economically and socially liberal opinion from Tony Blair to Margaret Thatcher) and the ‘Solidarity Party’ (a grab-bag for everyone to the left of Blair).

In reality – and with full PR in place – the centre and left of politics would break into more pieces than than two. For a more realistic take on Tim’s ‘Liberals’ see Paul Goodman’s post on what he calls the ‘Metropolitan Party’:

“Its core vote would be the young, urban and educated. Its house magazine would be The Economist. Its football team would be Chelsea. Its anthem would be City Lights. Its symbol would be the Shard (caricatured by its opponents with illustrations of Barad-dur). Sneered at by its opponents, it would sneer back.”

While one can imagine liberally-minded Tories and Orange Book Lib Dems joining forces under this banner, I think the Blairites would form a party of their own – let’s call them the ‘Progressives’. These would be more comfortable with redistribution and activist government than the Metropolitans – and a robust defence of enlightenment values could attract leftwing liberal interventionists like Nick Cohen.

I can foresee another party of the centre-left, which I’ll call the ‘Radicals’, who’d be the mirror image of the Progressives – pacifist instead of interventionist, civil libertarian instead of ‘tough on crime’, pro-conservation instead of pro-development and neo-Keynesian instead of fiscally conservative. This would be a natural home for left-leaning Lib Dems and the more moderate parts of the Green Party i.e. the ‘mangoes’ (green on the outside, but yellow on the inside).

As for the hard left of the Green Party, i.e. the ‘watermelons’ (green on the outside, but red on the inside), they’d be free to join up with other reds to form a new party to the left of where Labour is now. This would be a UKIP for lefties: anti-establishment, anti-capitalist and anti-western. It would be less clear as to what it was actually for, but that’s not a deal-breaker for people like Russell Brand and Owen Jones. Indeed, the vaguer the ideology the bigger the tent. In dishonour of Brand’s new book, we’ll call it the ‘Revolution Party’.

The Labour Party would therefore lose its rightwing to the Progressives and much of its leftwing to the Revolution Party. Further dribs and drabs would depart to the Radicals (especially ex-Lib Dems who’d previously switched to Labour) and the Nationals (Blue Labour types, hopefully). That would leave a substantial rump, which we’ll rename the ‘Unite Party’ – to reflect its exclusive focus on public sector vested interests.

That makes seven nationwide parties in all. There are other possibilities, but I’m only considering those likely to get more than five per cent of the vote. The big three would be the Freedom Party, the Nationals and the Unite Party with at least twenty per cent of the vote each – leaving the other four with up to ten per cent a piece.

Of course, it could all turn out rather differently. New Zealand has multi-party politics and a fully proportional system. And yet the main party of the centre-right – the National Party, as it happens – won a remarkable 47 per cent of the vote in this year’s general election. Not bad, eh?