The polls point to a range of scenarios on Thursday – we look at their consequences

BLUE HEAVEN

Conservative majority 80 or more

Shock factor: 6

This would be the best result for the Tories in the 30 years that have passed since Margaret Thatcher won a third term with a triple-digit majority in 1987. Comparisons between the Iron Lady and Theresa May will revive. The airwaves will thrum to Tory MPs saying: “I always had confidence in the prime minister.”

Often these would be the same Tories who had spent the time up until 8 June briefing journalists that an awful campaign had exposed her weaknesses as a leader.

A thumping majority gives May the scope to conduct a ruthless reshuffle of the government. That could be ominous for several members of the cabinet, including one or both of Philip Hammond and Boris Johnson.

She would also be liberated to stare down Tory resistance to her domestic agenda and pursue whatever course she chose in the Brexit negotiations, for good or ill.

This will have been another crushing night for the Lib Dems. After a campaign in which improvements in Labour’s poll ratings raised the hopes of pro-Corbyn activists, there will be deep shock to discover that their party has done excruciatingly badly. Calls from the party’s surviving MPs for Jeremy Corbyn to go and go immediately will be deafening.

AN IMPROVED MANDATE

Conservative majority 40 to 79

Shock factor: 2

If success is defined as outcome less expectations, then some Tories will be deflated by this result. Their frustration will be greater if the majority is at the lower end of the range. It will feel like a let-down after they started the election with the polls telling them they were on course for a landslide triumph.

That said, May will have led them to a better result than was managed by any of her five predecessors as Tory leader. This tops David Cameron at either of his two elections and John Major at his. Lynton Crosby, the Australian strategist who was given additional authority over the Tory campaign in its latter stages, will be happy to claim the credit for rescuing May in the final leg of electioneering.

Lynton Crosby’s futile attacks on Corbyn show he’s lost his touch | Chris Powell Read more

She will be reasonably insulated against backbench revolts over Brexit and her domestic agenda.

Labour will have lost seats and those losses will be substantial if the Tory majority comes in at the upper end of the band. Supporters of Corbyn would need some damn persuasive arguments to make a case that he should stay on or hand over to a successor of a similar ideological persuasion.

AS YOU WERE

Conservative majority less than 40

Shock factor: 4

This will be a severe disappointment to the Conservatives. There will be a lot of Tory fury directed at May for blowing what was considered a golden opportunity to build an impregnable majority. Her authority as leader will be badly compromised and it will be shredded if she has done worse than David Cameron two years ago. He and George Osborne would struggle to conceal their amusement at her distress.

A much diminished prime minister will have to be wary about firing ministers in a post-election reshuffle because she cannot afford to create too many enemies on her backbenches. She will also be vulnerable to backbench pressure from both the hard and soft Brexit wings of her party.

Smallish bands of Tory rebels can force a rethink on any government policy that they don’t like. The House of Lords will be harder to intimidate. An economic downturn in the course of the parliament could see May at risk of being toppled by her party.

Labour’s share of the vote will be a key bone of contention in arguments about Corbyn’s future. His supporters will argue that he is entitled to carry on, at least for a while, if he has improved on Ed Miliband’s 30% share in 2015.

LEFT HANGING

Hung Parliament. No party has a majority

Shock factor: 8

The Lib Dems used to dream of being kingmakers in this scenario, but after the punishment they took for their 2010-15 coalition with the Tories, they are shy of repeating the experience. Tim Farron, the Lib Dem leader, told the Observer at the beginning of the campaign that he would not go into coalition with anyone.

If the Conservatives are the largest party, and the parliamentary maths work, they might seek to carry on in government with life support provided by the Ulster Unionists. Even if the Tories did stagger on, May’s authority would be smashed. She has triggered an early election when she didn’t have to and thrown away the majority her party had won just two years previously.

If Labour were the largest party, senior figures suggest that they would try to rule as a minority government and dare other parties to bring them down. Labour will be reliant on some cooperation from the contingent of Scottish Nationalist MPs. A formal coalition with the SNP seems less likely.

Brexit negotiations will be even more horrendous for a prime minister operating without a majority. Another election before long would look like a very strong possibility.

JEZZ HE DID

Labour majority

Shock factor: 10

This result genuinely deserves to be called seismic. Even the polls most favourable to Labour do not suggest that Jeremy Corbyn is headed for Number 10. That would be an even bigger upset of expectations than the Brexit vote and the election of Donald Trump. Many, many people – including me – would have been proved absolutely wrong about the Labour leader’s capacity to win an election. A raft of previous assumptions about British politics will be torn up overnight.

Civil servants spend the hours after a Labour victory hastily scrabbling together outlines for the implementation of the manifesto. One of the cabinet secretary’s first duties will be arranging a briefing for the new PM on the nuclear deterrent. Then Jeremy Heywood will have to find someone who can remember how you go about nationalising things. Though Labour has not fully defined its position on Brexit, it would try to pursue a softer version.

The immediate challenge will be handling extreme turbulence in the markets as a massive sell-off of shares is accompanied by a plunge in the value of sterling. For the surprise victors, it would be a time of joy at confounding all those, including most Labour MPs, who never believed they could do it.