Deborah Mattinson looks at the General Election 2017 result and asks what actually happened and what does it mean for the future?

A Martian arriving in the UK and briefing themselves by reading the papers would conclude that Theresa May had been trounced and Jeremy Corbyn had won on June 8th. Tuning into Westminster gossip would only confirm that view. And yet the swing from Tory to Labour was just 2.0 per cent - smaller than the swing in 1992 when Labour lost and much, much smaller than the massive 10.2 per cent swing achieved in 1997. In fact, both parties actually increased their vote share (Labour up 9.8 per cent but Conservatives also up 5.8 per cent) as the Lib Dems declined by 0.5 per cent - despite gaining four seats – and UKIP’s vote collapsed by almost 11 per cent returning the UK to 1970’s style two party politics.

So what actually happened? When Theresa May stood on the steps of Downing Street to announce the “Brexit’ Election, voters in our focus groups agreed that we needed strong government to see us through difficult negotiations. Unusually, they knew little about either leader, providing considerable scope for change, but early views of Theresa May validated her “strength” positioning - they assumed she was Mrs Thatcher mark 2. Meanwhile, Jeremy Corbyn was seen as “well meaning but weak”: “a geography teacher” who voters struggled to envisage in No 10. This early advantage led to an out of control expectation management that would have made a comfortable majority look disappointing but rendered a poor result disastrous. As the campaign unfolded voters’ initial responses gave way to more informed judgement. The more they saw of Theresa May the less they liked her while Jeremy Corbyn leapt over the low bar fairly effortlessly.

The outcome challenges three long held tenets of campaigning and in doing so, confounded the political class of politicians, commentators and pollsters. Firstly, the expected result was based on an assumption about who votes – or, more specifically, an assumption that ‘didn’t vote in the last election’ means ‘won’t vote’ in the next one. This has been historically reliable and therefore led to pollsters underplaying younger voters and people who did not vote in 2015 in their weighting, arguably overcompensating for mistakes made in that election. Local activists from both parties, too, tended to focus on people who had previously voted and reported tales of Tory gains and Labour losses from the frontline.

Another conventional wisdom challenged is that campaigns and manifestos don’t make a difference. On this occasion, perhaps because the start point was such low knowledge of the candidates, the campaign did change minds. The manifestos, too, were noticed. Labour’s benefitted from a double PR hit due to being leaked a few days before publication, while the Tories’ foxhunting pledge, announced on its own, a week before anything else, also cut through. Scrapping tuition fees – a direct appeal to those younger voters stood out in Labour’s manifesto, while the ‘dementia tax’ – and its U-turn – were the best remembered from the Conservatives’, and may well have given otherwise loyal older voters pause for thought. As one wag commented “It was like One Direction calling their next album “Fxxx Off Teenage Girls!”.

Long-standing presumptions about the importance of the economy (It’s the economy, stupid!) were also questioned. BritainThinks’ work for Labour’s post 2015 Inquest revealed how lack of trust on economic management had been a major obstacle to voting Labour. In 2017 it was the dog that didn’t bark. Having tumbled down the ranking in polls on drivers of vote choice, it was rarely discussed by either party. Labour knew it to be a weakness and were unlikely to force the debate, while the Conservatives, trying to edge Philip Hammond out, preferred to exclude the Chancellor from the campaign by simply not referencing his topic. That said, voters certainly voted in their own self interest as the result shows, and, in doing so, reinforced the divisions by age, educational attainment, working status and attitudes that were first highlighted by the EU referendum.

One campaigning truth held good: that leadership matters above all else. It was the reason behind calling the election in the first place, the reason for the Conservatives’ “strong and stable“ positioning and, ultimately, the reason for Theresa May’s humiliation. But leadership in a campaign context is a relative thing. As May’s popularity plummeted, so Corbyn’s rose. As we first noticed in the 2015 Labour leadership contest Corbyn has a knack of making his opponents seem lacking in passion: stilted and wooden. One voter in a focus group observed, “She talks as if she’s swallowed her party’s manifesto,”. By the end, the consensus amongst voters and commentators alike was that Corbyn’s campaign had triumphed, while May could hardly put a foot right. However, our astute Martian will also notice that, although progress has been made, Labour trails the Conservatives by 56 seats and to win, will have to reach out beyond those enthusiastic youthful voters.

Deborah Mattinson is the founder of BritainThinks.

She tweets @debmattinson.