The EU referendum debate is now little more than a macho battle of the egos

Last night the leading presidential candidate for the Republican party used a televised debate to defend the size of his penis.

In what has to be one of the lowest points of the entire race so far, Donald Trump told Fox News that he could "guarantee" he had no problem with the extent of his manhood.

Watching a contest which is meant to be about the future of the biggest economic power in the world descend into a dick-measuring contest is fairly depressing.

Luckily, British politics has not yet quite descended to that level (although last week the prime minister and MPs exchanged 'your mum' jokes in the House of Commons, so let's not pat ourselves on the back too hard).

But when it comes to turning incredibly important debates about the future of the country into macho, ego-driven pissing contests, the EU referendum campaign suggests we're not really that far off from the American experience.

Last night one of the biggest egos in the contest, Nigel Farage, used a debate about the future of Britain's relationship to Europe and the world to pursue his personal vendetta against Ukip MP Douglas Carswell. In what appeared to be carefully considered remarks, Farage said that Carswell was "irrelevant" and insisted that he didn't care whether he left the party.

Carswell's crime was to join a different campaign group against the EU to the one officially endorsed by Farage. For a MP representing what is increasingly little more than a glorified personality cult, this was apparently one transgression too far.

"It would be better if Douglas Carswell saw the world the way we do [but] he doesn't," Farage said at the Ladbrokes referendum debate.

Asked if Carswell should leave Ukip, he replied: "He can do what he likes. I don't care. He's irrelevant."

He didn't quite say that Carswell was "dead to me" but if this was a gangster film, the Clacton MP would be checking carefully under his car before driving to work.

It's not just Ukip for whom the referendum campaign is now a personality contest. For the Tories as well, the question over whether we should become independent from Europe has become little more than a battle between two rather inflated egos.

On the one side is David Cameron, who has made himself the frontman of the campaign to stay in, and on the other side is London mayor Boris Johnson. For Cameron, Johnson's decision to back Brexit was taken as a personal "betrayal". As a result he devoted most of his speech in the House of Commons last week to taking chunks out of his former schoolmate. Since then, Johnson has returned the favour with repeated jabs at Cameron, who he accuses of "scaremongering" and spouting "baloney". As a result, the entire debate over the referendum has been dominated by the psychodrama between Boris and Dave and its impact on the upcoming Tory leadership contest.

In fact, much of last night's debate was also devoted to these questions, with Farage asked repeatedly about the impact of Boris and George Galloway's interventions on the campaign (Farage thought the impact of both was "huge", by the way).

Even Labour was dragged into it last night, with former Blair aide John McTernan devoting several of his responses to attacking Corbyn, who he said "wants to spend his time destroying the Labour party rather than saving the country."

As a result of all this macho posturing, the real question of whether Britain would be better off staying in or leaving the EU, is increasingly being left behind. The substantial debate about sovereignty, the economy and security are almost afterthoughts to the endless debate over which particular middle-aged, male politician is the biggest asset, or the biggest liability to the campaign.

And while none of the leading figures in the race has yet started comparing shoe sizes, it can surely only be a matter of time before the question comes up.