LONDON — With less than two weeks to go before the United Kingdom heads to the polls, there is still plenty of confusion about how the country’s political parties are targeting voters online.

Social media messaging. Viral partisan content. Digital attack ads. You name it — all of the U.K.’s parties are using them.

To cut through the noise, POLITICO teamed up with researchers from New York University.

The researchers pulled all the paid-for partisan ads bought by British groups on Facebook — which represent roughly 80 percent of all political messaging — from November 7 onwards, analyzing who was buying what in order to target which type of voter. (You can access their independent results here, based on the social network's transparency tools.)

Facebook does not provide a specific breakdown of money spent on these ads, only a range. So the academics calculated total spend by relying on the midpoint of the figures provided by the social networking giant. They also combined all the Facebook ad spending for the country's four main national parties (the Conservatives, Labour, Liberal Democrats and Brexit Party) from both these groups' main social media pages and those from regional and local affiliates to give countrywide totals.

POLITICO also crunched its own figures, based on Facebook’s transparency reports and CrowdTangle, a social networking analysis tool, to figure out how much each British political party had paid for each of its ads, as well as how successful both some anti- and pro-Brexit Facebook pages had been since early September at reaching would-be voters online.

The result is the most comprehensive overview yet of what is happening on Facebook ahead of the country’s December 12 vote.

As Facebook has increased its transparency efforts around political ads, it shows that partisan groups are aggressively turning to so-called organic content through pages like those mentioned below to reach would-be voters with messaging that often flies below the radar of existing digital transparency tools.

Here's what you need to know:

1) Most attention has focused on the activity of political parties. But third-party groups, including everyone from anti-Brexit campaigners like Best for Britain to non-partisan non-governmental organizations like Friends of the Earth, have significantly outspent traditional parties since the beginning of the election period on November 7. That’s particularly true of Momentum, the Labour-affiliated group, which continues to be one of the biggest third-party spenders.

This highlights a growing trend in the U.K. and beyond, in which groups loosely affiliated with mainstream parties are used to pump out partisan messaging ahead of elections.

The grey area between what is traditional political messaging and what comes from independent groups raises questions about how such funding should be monitored and regulated by countries’ campaign-financing rules.

2) Anti-Brexit groups — or those with ties to groups campaigning against the U.K.’s departure from the European Union — dominate third-party groups' spending, highlighting how the upcoming election, like or not, is considered by many as a quasi-Brexit referendum.

Facebook also requires non-political groups to publish when they are buying ads around specific hot-button issues like immigration and climate change. That’s why WWF UK, the activist group, is one of the biggest spenders because of its campaigning work around climate change. It also shows how despite Facebook's vocal efforts to improve transparency around who buys political ads on its global networks, the current tools leave a lot to be desired in terms of accuracy.

3) Unlike offline campaigning, which has focused on older voters, British political ad buys on Facebook have skewed young — not surprising when you consider that the number of Millennials with an Instagram account (the photo-sharing service is owned by Facebook) far outweighs those owned by people older than 35 years old.

Regardless of the age bracket targeted, groups have focused their money more on female voters than male ones, although that gender imbalance narrows as the demographics get older.

4) The Liberal Democrats and the Brexit Party are on contrasting sides of almost all policy issues. Online, that also plays out with how both groups are targeting voters. The Lib Dems, by far, have gone after young voters, earmarking more than two-thirds of their online campaign funds for voters under 35 years old.

The Brexit Party also wants the youth voter. But it has focused its significantly smaller financial resources on people older than 35 years old. The group similarly has put about three-quarters of the funds in paid-for messaging to target male voters. That’s significantly higher than the other parties, and highlights the Brexit Party's online strategy to win seats in the next U.K. parliament.

Who's making waves on Facebook?

5) It's difficult to know what messages are getting shared widely across the social network. But using these three pro-Brexit pages (Get Out Britain, Leave.eu and Political UK News) as a proxy, the amount of content promoting the U.K.'s departure from the EU — as well the times people have liked that material — has remained mostly steady in the build-up to the December 12 vote.

On the opposite side of the debate, anti-Brexit Facebook pages (Stop Brexit Ltd, The Daily Politik and Campaign to Remain) are having a mixed election, with the number of interactions on both Stop Brexit and Campaign to Remain falling slightly ahead of next month's nationwide vote.

That can't be said for The Daily Politik, a Facebook page that routinely promotes Jeremy Corbyn, the leader of the U.K.'s Labour Party, whose posts and likes have skyrocketed over the last two months as its backers have pumped out increasingly partisan material.

6) Alongside the data provided by NYU, POLITICO also took a look at the four main parties' political ad spending between October 28 and November 26, the latest monthlong period available from Facebook's transparency tools.

The Liberal Democrats stand apart from the other groups in their tactics. The party is spending most of its money on buying significantly more ads than its rivals to target very small groups of individuals in specific U.K. constituencies. Its average spend per ad is around £64, compared with £121 for the Brexit Party; £158 for the Conservatives and £170 for Labour.

Where Facebook did not provide specific figures for individual ad buys (on messages bought for less than £100), POLITICO took the editorial judgment of assigning those ads a value of £50, as that is the midpoint of what groups could have paid for the messages.

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