Matthew Goodwin is Professor of Politics at the University of Kent. He is the co-author of UKIP: Inside the Campaign to Redraw the Map of British Politics.

With the referendum campaign looming, all eyes will soon turn away from the renegotiation in Brussels and toward the ground war. For both the Remain and Leave camps, identifying their target territory – where they are most likely to find a receptive audience and get out their votes – will be key. In what looks set to be a close referendum race the ground campaigns could make all the difference.

But what are the real heartlands of the Eurosceptic and pro-EU movements? There are different ways of answering this question.

One method is to look in broad terms at the demography of each constituency, at the types of voters who reside in each seat.

There are especially good reasons for taking demography seriously. As other research has shown, the Remain and Leave votes are rooted strongly in some very sharp divides in British society.

While the Leave vote is anchored mainly in older, white, less qualified and more financially insecure voters, support for Remain is strongest among younger, middle-class and more affluent, degree-holding voters. This gives us something to work with.

For my book last year on UKIP’s general election campaign, written with Caitlin Milazzo, we ranked all seats in England and Wales according to their share of voters from these different social groups. This, in effect, left us with a measure of whether or not seats would likely be potentially receptive to the hard brand of Euroscepticism offered by the UK Independence Party. Take a look at the map below (you can also download the raw data here): this shows you where the key pockets of strength for the Eurosceptic movement can be found.

Matt Goodwin Map 1

As you can see, there is a clear geographical pattern.

Eurosceptics, for example, would likely meet receptive voters along England’s east and southern coasts, in clusters of seats in Yorkshire, the Midlands, around Cumbria and also Wales. When calculated this way, many of the top heartlands that are filled with voters who would likely be receptive to arguments for Brexit include Conservative-held seats – Boston and Skegness, Great Yarmouth, Waveney, Plymouth Moor View, North East Cambridgeshire, Louth and Horncastle, South Holland and The Deepings, and Blackpool North and Cleveleys. We calculated these rankings before the 2015 general election and it is worth noting that in many of these seats UKIP did go on to poll higher than average shares of the vote. All of these seats are filled with the blue-collar, older, financially struggling and less well qualified voters who we know are also among the most receptive to Euroscepticism.

Clearly, however, these seats look very different to those at the other end of the spectrum, where Eurosceptics will struggle to mobilize significant support. Affluent, diverse and London-based seats like Chelsea and Fulham, Hampstead and Kilburn, Poplar and Limehouse, Vauxhall, Tooting, Kensington and Putney are filled with voters who we would expect to turn out in large numbers for Remain. Beyond London it is also younger and more diverse urban areas like Bristol West, Cambridge, Manchester, Birmingham, Sheffield and St Albans that look similarly likely to deliver a strong vote for Remain.

But this is also only way to cut the numbers. We accept that looking only at these demographic factors is a rather crude measure, even if it has worked well in the past. If you download the spreadsheet then you can compare our ranking of seats based on demography with a different ranking compiled by another team of academics. In their innovative study, Chris Hanretty, Nick Vivyan and Ben Lauderdale considered a wider array of data, including information on how people actually said that they plan to vote at the referendum. Interestingly, however, there is still a strong overlap between the seats that appear in the upper third on both lists. Indeed, compare the map below, based on their work, with the one above.

Matt Goodwin Map 2

All but one of the ten most Eurosceptic seats in their study also appear in the top third of our own list, revealing how the two analyses point toward similar territory. In this second study, however, there was a greater concentration of Conservative-held territory in the top ten – Castle Point, Great Yarmouth, Christchurch, Blackpool North and Cleveleys, Boston and Skegness, South Holland and The Deepings, North East Cambridgeshire, Waveney and Aldridge Brownhills are all key hotspots for the Leave camp. Also in the top 50 are seats like North West Norfolk, Rayleigh and Wickford, Bognor Regis and Littlehampton and Mid Norfolk.

There are some clear patterns emerging. Across both rankings, between one in three and nearly one in two of the most promising seats for Eurosceptics are scattered along England’s eastern flank. Also, there are similar clusters of potential support in the Midlands, Yorkshire and North West, in struggling and left behind areas such as Blackpool, Bolton, Boston and Skegness, Don Valley, Dudley, Louth and Horncastle, Mansfield, Rotherham, Scunthorpe, Stoke, Walsall and Wigan.

It is also worth pointing out that while London looks instinctively hostile toward the Leave camp this is not true across the board. In more outer-east areas, such as Dagenham and Rainham, Hornchurch and Upminster and Romford there appears to be a receptive audience. In addition, it is also worth flagging some interesting opportunities for the Brexit camp in Wales where they may find a welcome in seats like Rhondda, Blaenau Gwent and Merthyr Tydfil, and where UKIP will no doubt be campaigning hard for the forthcoming elections in May.

So, there it is – hopefully a useful primer on what are likely to be the heartland areas for the various Leave camps going forward. And if you would like to do some more digging of your own feel free to download the data. Have fun!