Britain could take the road that leads out of Europe - or, to be more precise, the EU - in just 139 days' time. If that is to happen, who will drive the decision? The answer highlights some significant divisions in British society.
Prof John Curtice, pretty much the only poll watcher to emerge from the last election with his reputation enhanced, says that "those who want to leave the European Union are demographically very distinctive - most distinctive of all are those who have relatively little in the way of educational qualifications".
The figures from the most recent British Social Attitudes survey in 2014 are stark. Just 35% of those who have no qualifications want to remain in the EU compared with 78% of those with university degrees.
If you travel to Albion Street in the market town of Dunstable, Bedfordshire, it's pretty clear why. To many of the people who work here, the EU looks like a club that doesn't much want them as members. It appears to be run by wealthy, well-educated men in suits for wealthy, well-educated men in suits.
Julie McLeod, 46, who works at Brown & Wenman opticians, is typical of the sort of voter who could take us out of the EU.
"I'm a bit sceptical really of the whole Europe thing. I think they control too much of our laws," she told me.
"You want a situation where the British government can decide what the British government wants to do. We need a bit more say."
Julie, like many women voters, has not yet decided for certain how she'll vote. If Leave is to win, they need to convince many more people like her that the benefits of quitting outweigh the risks. Like so many others, immigration - and our government's inability to control it - is what bothers her most.
Next door on Albion Street, shopkeeper Tim Smart spells out how he believes the recent influx of migrants from Eastern Europe has affected him, his family and his town. He complains that those who come here have an unfair advantage as not only do they speak their own languages but they go to English schools and learn to speak English as well.
"If they then apply for a job for any supermarket or any position anywhere, who would you employ? Someone who speaks two languages or someone who speaks one language? My daughter has just had it in Northampton, funnily enough. It doesn't feel like a level playing field in my eyes."
Tim speaks for those who believe that immigration control is not simply a question of the country being too full, or of race or religion, but is a question of fairness.
It is people like him who David Cameron has in mind when he talks of ending "something for nothing" by limiting the in-work benefits EU migrants can get. It was a proposal that emerged from intensive polling and countless focus groups, although so far he's had to water the idea down.
Another sign that you may well be in favour of leaving the EU is your age. The older you are, the more likely you are to want to get out. It's an irony that the one group that have already had a vote on Europe - anyone aged 58 or older who could have voted when the last referendum was held in 1975 - are precisely the people who now want another chance to reverse the decision taken back then.
The British Social Attitudes survey shows that almost half - 46% - of those over 55 want to get out while half that number - 23% - of those under 35 agree with them.
Speaking to Kenneth Spinks, who's 85, you get a sense of why. He feels that he was invited to vote to join an economic club in which it was easier and cheaper to buy and sell things - the Common Market as it was known then - and has instead found himself governed by a big, bossy, bureaucratic organisation in Brussels.
I spoke to him in the local Conservative Club. One more sign that you might be a Leaver is that you voted Conservative at the last election. Tory voters are much less likely to be pro-EU than those of other parties - other than UKIP, of course.
That is why the draft deal David Cameron unveiled this week matters so much. Many Conservative voters - the people who backed the prime minister just last May - will be inclined to follow his lead just as Labour voters followed Harold Wilson's back in 1975.
Kenneth couldn't have been clearer that he wants to quit Europe until we had this exchange.
Me: "You're a staunch Tory man, but even if the Tory leader says, 'I want us to stay in, I think it's in the best interest of the country,' you'd vote against him, would you?
Kenneth: "Well, it's all according to what he'll come back with. If he'll come back with something that's really good, it might sway me a bit."
Take a few more paces along Albion Street and you'll find the last crucial group of potential "leavers" - small businesspeople who, unlike those who run big companies, don't export to Europe but do still have to put up with its rules.
Aaron Lee, 28, who runs Lee & Sons Cleaning Services, says: "All we're doing is paying out fortunes of money to join this trading union, and being told what we can and can't do.
"For example, we can only use a certain power Hoover because they've governed the power rating down. Where we could Hoover a floor in an hour, it's now going to take us two."
The Leave campaign cannot win simply by building a coalition of old, non graduate, self-employed voters. They will need - and, indeed, already have - support from younger, well-educated people who work for big businesses too. However, it is these divisions in society that could determine the future of our country for decades to come.
Matthew Price's report for the Today programme on which voters are most likely to vote for the UK to remain in the EU was published on 24 February 2016: The view from Colchester.