The corruption of US politics shows why the UK is right to limit electoral spending

Perhaps £675,315 doesn't sound that much in the context of a nationwide referendum. After all, there are an estimated 46.8 million people on the UK electoral register. So the illegal additional spending in 2016 by the Vote Leave campaign, above its official £7m limit, amounts to around 1.5p per potential voter. That barely stretches to the cost of printing a leaflet.

When the information commissioner fined Facebook £500,000 earlier this month for failing to safeguard users' data in the same referendum, many remarked on how unjustly small the bill was. So why the fuss now about a roughly equivalent sum?

To understand, cast a fearful glance at the US, where there are no limits on what political parties and individuals can spend in the pursuit of winning elections. According to the Centre for Responsive Politics, the average winner of a seat in the House of Representatives spent $1.5m on his or her campaign in 2016.

But that's chump change compared to the cost of getting into the Senate. The average winner of a berth in the upper house that year spent $12m, a new record. And this is a lower bound estimate. When one factors in spending by "political action committees", the average bill doubles.

The degree to which unlimited campaign spending has corrupted US politics is difficult to overstate. As the above figures show, to sustain a career in politics requires copious amounts of funding.

And that funding comes, in large part, from corporate vested interests or the ultra-wealthy. It comes, directly or indirectly, from the very firms and individuals affected by the legislation produced by members of congress.

And it is getting worse. The Supreme Court in 2010 ruled, by 5-4, that it was an unwarranted curb on "free speech" to limit the sums that corporations can spend on political attack and candidate promotion adverts.

This has led to an explosion of "outside" political spending over the past eight years.

Much has been made of the fact that Trump's 2016 campaign spent less than those of several of his Republican predecessors, and only 60 per cent of the $1bn outlay of Hillary Clinton's, prompting some to suggest money is less important than it used to be in winning US elections.

But there were special circumstances here. The reality TV star Trump was given a vast amount of free air time by television news networks, who, in a cynical pursuit of ratings, broke their own rules which prevent candidates giving interviews over the phone, rather than face to face.

Moreover, one now has to understand Trump as part of a system, rather than as an individual maverick. As the economist Paul Krugman points out, Trump is sustained in office, despite his many impeachable offences, by a broader Republican Party, which is obsessed with a donor-friendly agenda of tax cuts and deregulation.

The 2016 congressional elections still set new spending records of $4bn, up 3 per cent in real terms on those in 2014 and 70 per cent higher than the outlay in 1998. This year's midterms are not expected to buck the trend. And studies suggest that around 90 per cent of the time, the better-financed candidate wins.

Nor is this capture of politics by mega money popular. Polling suggest that two-thirds of Americans support limits on campaign spending. Even most Republican-leaning voters agree.

Yet the prospect of any change in an era of cowed and corrupt congressmen, a Supreme Court tilting ever more in a corporate-libertarian direction and a pluto-populist president who is scornful of existing democratic norms (let alone shoring them up), the prospect of change seems as likely as Trump voluntarily releasing his full tax returns.

Yes, £675,315 might not sound like a king's ransom. But the principle of heavily policed limits on the influence of big money in our politics is priceless. It's right we defend it jealously - even obsessively.