It’s a serious question: what do we think needs to happen for the Lib Dems to become the official opposition within the next 10 years? What are the circumstances, and which are the ones we have the control to influence?

In posing these questions, I’m making three assumptions. First, and most importantly – so the question doesn’t get brushed aside as hopelessly unrealistic – it won’t happen overnight. However wounded the Labour party currently is, it still has six times as many MPs, and three times more members, than the Lib Dems. It also has a core vote, diminished and diminishing, but resilient and not to be underestimated.

My second assumption, however, is a counterweight to this: it’s an entirely realistic proposition for the Lib Dems to overtake Labour. After all, the Lib Dems have bested them in the BBC’s nationally-projected popular vote in three sets of recent local council elections: in 2004, 2006 and 2008. Now, of course, the popular vote in local elections is one thing; the national vote in a general election is quite another. But still.

The third assumption: the Lib Dems are not about to usurp the Tories. The only party we can plausibly hope to displace in the next two Parliaments is Labour. Perhaps – perhaps – it might have been possible to overtake the Tories in 2003, when they were at their IDS-nadir. But the Tories got their act together sufficiently to scrape themselves off the floor, while the Lib Dems failed fully to capitalise on our ‘Iraq bounce’, and convince the public that we were robust enough to be a government-in-waiting.

With these assumptions in place – that the Lib Dems can come second, if not immediately, and that it would be Labour who are pushed into third position – let’s actually try and answer the big question: what are the conditions which can generate such a perfect storm? Here are my top three:

Maybe it’s wrong to start with an essentially negative pre-condition, but I think it’s a candid truth. The split at the top of the party between Asquith and Lloyd George contributed – to what extent remains a moot point – to the eclipse of the Liberals by Labour in the last century. I suspect it will need a similar schism within the Labour party for the Lib Dems to push through into second place in this century.

The good news is that this is quite plausible. The Labour party has been turned inside-out over the last 15 years. The socialist ideology which once inspired it has been abandoned (state ownership might be experiencing a temporary resurgence but it’s borne of last-ditch necessity, not principled design). The progressive, small-l-liberal, internationalist outlook embodied by social democrats like Roys Jenkins and Hattersley has been junked in favour of the harsh, reactionary populism exemplified by David Blunkett and Phil Woolas.

New Labour has no ideological centre of gravity – what matters is what works. It’s raison d’etre was to win elections. Once that habit ceases, what will be its purpose? The leadership battle to succeed Gordon Brown will determine the extent to which the Labour party remains relevant to national political debate. Choose wrongly – as the Tories did, first with William Hague, then, almost fatally, with IDS – and Labour may drift even further down in the polls.

If the Tories are here to stay – and, let’s be honest, there is likely always to need to be a political home for those folk who want things to remain pretty much as they are, either because they’re doing very-well-thank-you out of the established system, or because they’re scared of the alternatives, or both – then the role for the Lib Dems is clear: we need to show we can be a reforming, progressive government. I’ve discussed before the problem the party has in defining its unique selling point: the Tories are there to help the rich, and those who aspire to be rich; Labour is there for those who are poor, or fear they might one day be poor. Who are the Lib Dems there for?

My answer: we’re there to champion the underdog. ‘The underdog’ is distinct from ‘the poor’ because it recognises (as Labour rarely does) that people are not powerless solely because of their lowly economic status.

The Lib Dems stuck up for the Gurkhas’ right to UK residency not because they were poor (though doubtless some of them are) but because we believed the government should stand by the simple principle that those who are prepared to die for this country should be able to live in this country. The Lib Dems stuck up for the G20 protestors not because we necessarily agree with them, but because we believe the state – both government and police – is undermining the right to peaceful protest, an essential component of a civilised, pluralist, democratic society. And the Lib Dems stuck up for the rule of law when both Labour and the Tories joined forces to back the war against Iraq on a flimsy pretext, and against the will of the international community.

To begin with, each of these causes was a minority issue, potentially even an unpopular issue, and could have rebounded on the Lib Dems. But we stuck to our guns, and gave a voice to the powerless, championed the underdog. Which is why I believe the Lib Dems are the most truly progressive force in British politics.

3. The Liberal Democrats need to show how we will govern.

This has always been our weak spot. Not only do too many people think that a vote for the Lib Dems is a wasted vote, more importantly too many fear that if a Lib Dem government were to be formed we’d prove ourselves to be weak and insufficient. We’re nice guys, but ultimately too polite, lacking that inner core of ruthlessness which voters may say they despise in their politicians but are actually, deep down, reassured by. The one time in recent history we attempted to be ruthless – when Charles Kennedy was defenestrated – our conflicted MPs made a mess of it: the party no longer looked nice, but we had proven it just wasn’t in us to be efficiently ruthless.