This Map Shows Why A Pro-EU Party Might Flop At The Next General Election

    The country was almost evenly split in the referendum – but that's not how it would play out in a general election.

    As we all know, the result of the EU referendum last week was pretty close – less than 4% in it.

    That's given rise to lots of people speculating that a party which ran on a "keep us in the EU" ticket in the next general election could have a real shot – whether that's a current party, a "progressive alliance", or a whole new pro-EU party. In particular, it's likely to be a debate the Labour party will have during any leadership contest.

    But... things aren't that simple. Things are never that simple.

    To see how the country's referendum vote could affect a general election, we've translated the referendum results (which in England, Scotland and Wales were counted by council area, not constituency) into results broken down by parliamentary seats.

    And when you do that, you get a radically different outcome. Instead of a close result, Leave win in a landslide.

    Although the referendum result was close nationally, Remain piled up many of its votes in a relatively small number of constituencies (London and Scotland being prime examples). As a result, the UK's first-past-the-post electoral system would produce an extremely skewed result.

    In our projection, Leave would win 421 seats across the UK, while Remain would win just 229.

    That's a majority of 192 for Leave – larger even than Tony Blair's majority in the 1997 Labour landslide. The message is stark: most prospective MPs at the next election will be standing in constituencies which voted to Leave.

    Some caveats about how we did this: especially for large council areas that both had very close results and contain lots of constituencies, this won't be accurate down to the individual constituency level. For some specific constituencies – for example, wealthier pro-Remain constituencies in otherwise anti-EU cities – it might call them wrong. But because data wasn't consistently collected across Britain about how individual wards within each council voted (although some areas did), we can't be sure of how voting patterns changed across each council area.

    This means that, for example, Birmingham's ten constituencies are all assigned a narrow Leave win, while Leeds' eight are all narrow Remain. That's unlikely to be exactly how it would play out in reality – but equally, we believe it balances out when looking at nation-wide patterns.

    That's backed up by the fact that political scientist Chris Hanretty conducted a similar exercise using a more complex methodology, and he came out with a very similar result: looking at just English and Welsh constituencies, he predicted that 421 out of the 574 would have voted Leave. (Our count includes Scotland and Northern Ireland as well.)

    This gives both Labour and the Conservatives problems – but Labour's troubles are potentially much more severe.

    On the map above, you can use the tabs at the bottom to switch between the referendum result, and a map of each party's current seats. It also shows each party's potential target seats – the marginal constituencies they'll need to take if they want to win the election.

    This is what it looks like when you compare the referendum results to Labour's current seats (dark red) and target seats (light red).

    You can see that while most of Labour's seats and targets are in Leave-leaning areas, a significant number are in the big, heavily Remain-voting cities – notably London, Manchester, and Liverpool.

    If you break down Labour's current seats, they work out at 150 Leave, 82 Remain – roughly a 65% to 35% split.

    Meanwhile you can see the Conservatives current and target seats are a bit split, but nowhere near as much – their heartlands (unsurprisingly) are mostly solid Leave territory.

    The Tories' constituency breakdown is 258 Leave, 72 Remain – over 78% of their current seats are in favour of Leave.

    So what does this mean?

    It means that if Labour wants to win the next election, the majority of seats it will need to win will be in Leave-voting areas – often quite strongly Leave-leaning.

    Here are the seats Labour lost by the closest margin in 2015, and how they voted in the referendum. The further above the horizontal line they are, the stronger they voted for Leave.

    Obviously people vote on many issues in a general election, not just one. But it does suggest that a Labour party with a manifesto commitment to reversing Brexit might have a stuggle winning these vital seats. That's especially true if a snap election is called in the next six months or so – before any likely economic effects of Brexit on jobs, housing and the cost of living have really kicked in.

    But it's not that simple for Labour – they've got to defend seats they already hold as well. And the seats that they won narrowly last election show a slightly more even split between Remain and Leave.

    With the Lib Dems announcing they will run on a strongly pro-EU manifesto, they might be able to cause a less EU-friendly Labour some problems in all those marginal seats below the horizontal line.

    (These scatter charts focus on English and Welsh consituencies only. As Scotland voted so strongly for Remain, which the SNP backed, it seems unlikely that their current dominance will be impacted by the EU referendum. If Labour have to appeal to pro-Leave areas of England and Wales as well, that could make a Scottish Labour resurgence even harder work.)

    The Conservatives, meanwhile, only have a few pro-Remain seats that they currently hold by small margins.

    That makes their job a lot easier – given they're defending a majority, they don't need to worry much about appealing to Remain supporters. (And let's be honest, there's currently no realistic prospect that the Tories will run on a pro-EU ticket in the next election, even if Remain supporter Theresa May does end up as their new leader.)

    The conclusion: if the next election is dominated by the issue of the EU Referendum, which seems a decent bet, it's going to be very hard for a pro-EU party to win without there being a major change of heart about the EU across large swathes of the country.

    Now, there's some evidence that might be happening to an extent (if you trust polls, lol) – but probably not by enough yet to make a difference.

    EU referendum poll: Remain: 45% Leave: 40% (via BMG / 29 - 30 Jun)

    And unless that change of heart happens, Labour have a much, much trickier path to tread – while the Tory heartlands strongly back Leave, Labour's heartlands are split between a majority of Leave seats, and a sizeable minority of strongly pro-Remain seats in major urban areas.

    There is one interesting possibility for EU fans, though. As we saw in Scotland, a referendum has the potential to entirely redraw the political map in subsequent elections.

    That could get interesting for the pro-Remain seats in the south of England outside of London – most of which, as you can see here, are traditional Tory heartlands.

    Does the existence of this large pro-Remain southern bloc offer a small glimmer of hope for despairing Remain backers? How much do voters in these places care about Remain? Could it be enough to flip their vote away from a Conservative party that, maybe, they would blame for taking us out of Europe?

    On their own, they wouldn't be enough to win an election... but could they throw Labour, or the Lib Dems, or that hypothetical new pro-EU party a lifeline?