Democracy everywhere is facing serious challenges.

The United States is gripped by the most bizarre presidential primary campaign in living memory, with populist outsiders threatening to topple established party machines.

Brazil is paralysed by constitutional crisis.

Europeans trace their malaise to a democratic deficit in the European Union. And in the United Kingdom, the vision of recovered national sovereignty is fuelling the campaign to leave the EU.

But efforts to restore the “power of the people” can easily end up turning the people against each other.

The upcoming referendum on Britain’s EU membership is a case in point.

Traditional theorists of representative democracy are deeply sceptical of direct democracy.

Referenda, in particular, can carry serious risks. As a complex issue is boiled down to a binary choice, that choice becomes existential — a potential source of deep long-term divisions.

That is precisely what is happening in the UK today.

But there is no escape from complexity in the British campaign; it simply re-emerges in the uncertainty surrounding what a vote for either camp would actually mean.

Remaining in the EU could mean retaining a “semi-detached” status, and perhaps seeking more exemptions and opt outs from common rules — the course that Prime Minister David Cameron would seem to prefer.

But it could also mean trying to address on a collective basis a broad range of issues — from security to refugees to economics — that, as pro-EU campaigners point out, the UK cannot resolve on its own.

This outcome, of course, would involve greater integration.

The implications of voting to leave the EU (“Brexit”) are even more obscure.

What would happen if the UK were to embark on the two-year exit process mandated by the Treaty of Lisbon?

Could it work in the existing European Economic Area (the so-called Norwegian solution)?

Or should it pursue a host of bilateral agreements (the “Swiss solution”)?

What about — as Michael Gove, Cameron’s justice minister, has suggested — establishing a free-trade zone with Bosnia, Ukraine  and Albania (the “Albanian model”)?

Should the UK engage in negotiations for the Transatlantic Trade and Investment Partnership as a separate partner?

Could the UK reasonably put its faith in rapid global progress in dismantling tariff barriers?

So the yes/no vote on June 23 will resolve nothing. But the problem does not end there.

Negotiating the details of Britain’s relationship with Europe, whatever the outcome, will take years; but ameliorating the polarisation caused by the referendum will take even longer.

For countries like Switzerland, which practise true direct democracy, referenda do not tend to produce deep polarisation.

Because they occur very often, winning coalitions shift over time and from issue to issue, which means that no single vote leaves deep cleavages in the electorate.

But in representative democracies like the UK (and nearly all other democracies today), voters choose leaders to weigh up complex arguments and make tradeoffs.

When a decision is deemed so vital that it cannot be trusted to the representatives, the principle that underlies the entire political order is challenged.

Moreover, it takes on a momentous quality, fuelling intense opposition between sides.

Indeed, the deep polarisation resulting from the Brexit referendum recalls previous episodes that shook up political allegiances and broke up old friendships.

The most recent analogy in the UK is the Suez Crisis of 1956, which turned into a debate about post-war Britain’s role in the world and the extent of its dependence on American goodwill.

In the 19th century, there was an intense debate over free trade in grain, which culminated in Prime Minister Robert Peel’s repeal of the Corn Laws.

Fifty years later, France was torn apart by the prosecution of army captain Alfred Dreyfus for treason.

In each of these defining political debates, each side has demonised the other, claiming that the opponent is driven by malice or ignorance.

The same is happening in Britain today.

Britons, who want to stay in the EU, are derided as slaves to an unaccountable international technocratic bureaucracy, traitors to their country who can win only by unleashing “project fear”.

Meanwhile, advocates of continued EU membership portray their opponents as obscurantist, ill educated, know nothing little Englanders, driven solely by anger and fear. In other words, each side argues that the other is incapable of tempering emotion with rational thought.

The reality is that all of the EU-related questions spurring anger and fear among Britons today could be addressed on a case-by-case basis.

In response to concerns that migrants will strain education, housing, or transport, one might make the case for better schools, more planning permission, or increased infrastructure investment.

In all these areas, elected representatives are well placed to adjudicate the trade-offs required.

By turning to the mechanisms of direct democracy, Britain has undermined its capacity to address the challenges it faces in a manner that promotes stability.

An all-or-nothing situation is driving citizens increasingly to view politics in terms that the German legal philosopher (and Nazi party member) Carl Schmitt considered inevitable: the distinction between friend and enemy — between those for whom one is ultimately willing to die and those whom one is ultimately willing to kill.

Such divisions can be bridged only by the passage of (a lot of) time. They can endure beyond the circumstances that gave rise to them, often taking several generations to fade away.

For example, Mediterranean Europe is still wracked by debates about the power of the Catholic Church, just as the American south continues to bear the legacy of slavery and the Civil War.

The result is social tensions, political blockage and an inability to reform or modernise.

By calling a referendum, Britain has introduced a deep and fundamental conflict into its political sphere. It is now in real danger of becoming an irreconcilably divided and increasingly stalemated society.