British politics is falling apart. I mean literally. Political parties are fragmenting, opinion is hardening, and the vicious volume of some arguments feels like it could split society into ever tinier tribes.

Why? It can’t just be technology. Or particular individuals. And no, it’s not just Brexit.

Division between us is connected to a growing separation in the way we tackle ideas, which is partly by design. Sharp focus can win short-term campaigns – just look at Brexit itself. Wedge issues are seen as currency, and divisiveness has become part of political life.

However, single issues aren’t enough to win a majority, and certainly not in a sustainable way. In my experience, you reach a clear limit to a single idea, regardless of the accuracy of your initial insight.

When I was 25 I started a political campaign. Back in 2014 it was clear that the logic of sustainable government funding, that’s to say balancing the long-term finances of government, was being confused with the ideological opinion of a small state. So with a few friends I decided to claim the phrase ‘Balance the Books’ for its true meaning. There was a gap for a very specific voice and we even had some success in the media. But we didn’t change the future course of government finance, or the way people think about political decisions.

In hindsight, there are probably a few reasons why. Our idea to never need austerity was confused with the argument for it. Even though the whole campaign was about connecting decisions with their consequences, we focused too much on the single issue of the deficit.

This had three clear lessons, all of which have strong parallels in today’s politics.

First, real world issues aren’t simple. Nobody ever shouted themselves hoarse about public accounting reform. But they might do so about pensions cuts or the intergenerational unfairness of student loans. We missed so many tricks.

In a similar way, today’s Labour Party risks obsessing about inequality in a relatively abstract sense, and not talking enough about school meals, or access to the best careers, or racism. The SNP is known for one key policy… at the expense of others. Likewise Change UK never explained how they would change the UK. Single-issue politics can’t beat detail.

Second, teamwork needs breadth of experience. We all have different reasons for campaigning together on the same platform. I didn’t launch sub-campaigns about student loans or state pensions because I hadn’t persuaded an expert on the issues to get involved. Even a brilliant team of half a dozen dedicated friends won’t get you very far.

Today’s Conservative Party springs to mind, where banging on about Europe has created a so-called team divided on their supposedly signature issue, and dangerously distracted from their shared responsibility as the (current) party of government. Complementary ideas can bring together complementary skills for a diverse and effective team. Single-issue politics just can’t hold a good team together.

Third, single issues don’t last. In my experience, the deeper principles of fundamentally sustainable and long-term government were lost as our core issue of the government’s balance sheet slipped down the agenda. For what it’s worth, the deficit stats look better, but we still haven’t solved the problems that led to a sharp correction and the pain of austerity – and there is a risk of even bigger problems in future as our society ages. Time can be a powerful ally, and adaptability is the only way to make the most of it.

Today, the party that needs to be wary of this the most might be the Liberal Democrats. I even say this now as a member. Brexit might be a brilliant rallying cry, but it isn’t going to last forever, whatever the outcome (or how it might feel…). I haven’t yet seen a complete vision of what the Liberal Democrat future would be, instead of Brexit. Single-issue politics wears thin.

None of this is to say that single issues don’t matter. We should all care about causes that count and milestones do matter. But freeing Nelson Mandela wasn’t the same as ending apartheid. Winning an election isn’t the same as delivering what you promised. There’s a risk of confusing campaigns with movements.

So the bad news is this: a political culture that focuses on single issues acts like a first-past-the-post system for ideas. In a competition for the number one issue, people will naturally disagree far more than they would if able to choose between smorgasbords of policies. We used to call them manifestos.

But what’s the good news? Single-issues will eventually lose – to detail, teamwork and time.

With a General Election looking ever closer, this presents an enormous opportunity for a workable manifesto to govern the UK. It’s time for joined-up thinking and believing in better.

Adam Kirby is a former director of Balance the Books and a member of the Liberal Democrats