It has become a commonplace to complain that the argument about Europe has become too shrill, coarse and divisive. To which I reply: what exactly did you expect? The stakes are vertiginous, the consequences will reverberate for decades and the argument goes to the heart of what kind of country we want the United Kingdom to be and whether there will still be a United Kingdom should the decision be for Out.

It is in the nature of the beast to be shrill, coarse and divisive. The referendum is a binary device. It does not permit of nuance and refinement. It is polarising by design. Some people already know exactly how they will vote. They have always known. Many others will lean 60/40 towards In or sway 60/40 for Out. I suspect that describes the feelings of a lot of voters. But you can’t play percentages on the ballot paper. It demands the taking of sides. That is the simplicity and the brutality of a referendum. This was never going to be an exercise in Socratic dialogue. If that is what you are yearning for, you will need to persuade Doctor Who to lend you his time machine and whisk back to ancient Greece. Where you may be disappointed to find that politics was not always decorous in antique Athens. Socrates’ life was terminated by his trial and execution.

A better reason for anxiety about how the campaign has unfolded is the uneven way in which the passion is distributed. There are segments of the public who feel as animated as the political classes, but on the evidence so far they are very much a minority. All the heat generated by the campaign is leaving a lot of voters feeling cool. There is a conspicuous absence of the excitement and engagement that energised the Scots when they debated their future in the independence referendum two years ago.

If this is of advantage to one side of the argument, it is most likely to be of benefit to the Outers. One of the few things that everyone agrees on is that a low turnout tilts the outcome in the direction of Brexit. If the committed Outers turn up on the day of decision and reluctant Inners remain at home, then Leave has its best chance of victory. Conversely, the higher the turnout, the more likely it is to mean a decision for Bremain. It is some encouragement to the In cause that the proportion of the Europe-friendly young saying that they will definitely cast a ballot has been nudging up, but their overall inclination to vote remains considerably lower than among their older, more Europe-hostile grandparents. Note to those who have yet to register: the deadline is midnight on Tuesday.

In its final, most intense weeks, the campaign will boil down to the economy and immigration. The Inners will relentlessly emphasise the risks to trade, jobs and investment posed by a vote to leave. Ask David Cameron any question between now and 23 June and he will reply: “Leaving would be an act of economic self-harm.” Would you care for a cup of tea, prime minister? “Leaving would be an act of economic self-harm.” It is Remain’s core argument and Leave’s most acute area of weakness. I thought Michael Gove put in a generally accomplished performance for the Outers in the debate staged by Sky, but he gasped like a beached fish when challenged to name a single international body or allied country that thinks Brexit is to be recommended. He floundered because there isn’t one.

The Outers will continue to complain that their rivals are running a Project Fear while trying to trump it with their own Project Scare. Unable to plausibly reassure that Britain wouldn’t take economic damage from a decision to depart, the Outers now seek to paint continuing membership as the more hazardous choice. That has led them to shovel nearly all of their chips on opposition to immigration. If their pitch is condensed to a sentence, it is “slam the door on foreigners”. In terms of the internal arguments about strategy between the Outers, this is a vindication for Nigel Farage. He has always contended that this was the way for his side to win. The Ukip leader can be forgiven a smirk of satisfaction that the Tory Brexiters who used to sneer that he was “toxic” are now doing karaoke versions of his tunes.

Immigration is the most potent fuel of hostility to the EU. So every day that the conversation is mainly about immigration can be counted a profitable day for the Outers. Fear of what Brexit would mean for the economy is the sharpest weapon in the armoury of In. So every day that the conversation is mainly about the economy can be chalked up as a good day for the Inners. If the last week has felt rather better for Out than In, it is because the news agenda has been driven more by immigration than economics.

With fewer than 20 days to go before the moment of decision, there are still a lot of unsure voters out there. The barrages of claim and counterclaim have left many feeling not enlightened, but shell-shocked. “I’ve seen no valid facts at all,” complained the young woman who had a pop at David Cameron during his encounter with the Sky audience.

Iain Duncan Smith campaigns for Vote Leave. Photograph: Nigel Roddis/EPA

The uncertain voter is often to be heard asking for “more facts” or “facts that I can trust” as if there were some divinely impartial entity available to guide the choice. A strategist on the In team says he hears a constant refrain from the samples of voters that he talks to. “Within five minutes of starting a focus group, the word ‘confused’ will have been used 30 times.” This was probably to be expected. Europe is an issue that has only ever galvanised a minority of the electorate. Most folk have had better things to think about than the precise mechanics of Article 50 of the Lisbon treaty. David Cameron did not pledge this referendum as a means of educating the country about how the EU works and holding a great national debate about our place in the world. He came up with it as a device to contain and, or so he once hoped, resolve his party’s divisions. How is that working out for you, prime minister?

All the poisons that have suppurated within the Tory party for so many decades are boiling to the surface. In February, when the starting gun was fired, both sides made pious declarations that they wouldn’t let it get personal. I treasure a quote from Iain Duncan Smith urging the Tory party to conduct a good, clean fight. “Do not play the person, play the ball,” intoned this choirboy. A few weeks on, the same Iain Duncan Smith calls Mr Cameron “Pinocchio”. Why skulk behind euphemism, Iain? The Tory party has drunk so deep from the well of venom you might as well say what you really mean. You might as well come out and directly call your leader a liar.

In David Cameron’s circle, there is burning rage about the way some leading Tory Brexiters have conducted themselves and a thirst to take revenge if the prime minister wins. That is fully reciprocated among those Outers who already plot to depose the man who won them an unexpected election victory just a year ago. These Tory games are highly compelling for everyone in the media, who love blue-on-blue action. There was a certain inevitability that the campaign would be like this. David Cameron, as the author of the referendum, was bound to be the de facto leader of Remain. Once Boris Johnson had come out for Out, he was going to be treated as the de facto leader of Leave. The Out campaign understands and exploits the journalistic appetite for seeing Tories at war with each other. The Outers have been quite cute about using senior Tories to launch direct attacks on the prime minister both to undermine his authority and to generate news coverage for their claims. It has been a frustration for the In campaign that David Cameron doesn’t want to reply in kind. With the debate so dominated by figures from just one party only occasionally are non-Tory voices to be heard through the cacophony of the clash between rival factions of Conservative. This is surely at least some of the explanation for why so many voters are feeling untouched, unmoved and unconvinced by either side. Too much of the argument is being conducted as if this were the Eton Wall Game, an arcane and violent sport played only by the tiny number of expensively educated people who have been taught the rules.

This places a big responsibility on the leaders of other parties representing the many millions of people who don’t identify with the Conservatives. Most of Britain is not Tory. The voices of non-Tory Britain need to be heard much more strongly. Now is the time for them to get really stuck in. There is also a responsibility on the broadcast media to be sure that non-Conservative voices are given their fair share of airtime.

This isn’t some kind of Tory game of thrones. The question being asked is not whether David Cameron or Boris Johnson should be prime minister. This is far, far more important than that. Everyone’s country is at stake.