When Theresa May decided to go for an early election, she transformed the nature of her premiership. Up to that point she had been the steady hand on the tiller, righting a ship of state buffeted by the Brexit referendum. By going to the country to win her own mandate, she sought to become more than that. She wanted her own sizeable majority and, in so doing, invited comparison with the two prime ministers who have done the most to shape modern Britain: Margaret Thatcher and Tony Blair. She was asking to be judged against their electoral triumphs.

At the start of this campaign, May looked comfortable in this company. The polls suggested that she would get a higher vote share than either Thatcher or Blair and win a majority to stand any comparison with their landslides. As the campaign has gone on, this has looked less certain. The 20-point Tory leads at the start of the campaign are a distant memory. They’ve been replaced with polls suggesting May’s majority could be smaller than David Cameron’s. The Thatcher and Blair comparisons are no longer flattering.

James Forsyth and Tim Shipman ask whether anyone's a winner in this campaign:

These recent polls are almost certainly wrong. Those on the ground say that it feels far more like the Tories have a 12-point lead and are heading for a majority of about 80 seats. But there’s a reason why single--digit poll leads are being given credence: this campaign has not been the choreographed coronation that many were expecting. On the contrary, it has exposed weakness in May’s methods and in her policies.

Theresa May is certainly making history: never before has a party leader had to abandon a manifesto pledge before an election. But the debacle over the so-called dementia tax has been made all the worse by the absence of any real offer in the manifesto. Candidates complain that it is hard to explain, on the doorstep, what voters will actually get if they vote Tory. They lament that, beyond the Miliband-like cap on energy bills and the focus on technical education, it is hard to say what Theresa May is doing for the ‘just about managing’ classes that she speaks about so much. There is grumbling that she and her team are better at diagnosing problems than solving them.

It’s not that she has no philosophy. Her vision of a third way between globalism and nationalism is important. Without it, politics could turn very ugly — just look at the continent, where populist parties are still advancing. But the Tory manifesto suggests that Mayism is now more of a rhetorical approach (‘We do not believe in untrammelled free markets. We reject the cult of selfish individualism’) than a developed policy agenda. Indeed, the striking lack of policy detail suggests that the May team really weren’t planning for an early election.

This lack of hard, well-thought-out detail has caused problems. Staff at Conservative Campaign Headquarters say that the inability to say who, other than the poorest, will still get the winter fuel allowance is a sticking point in many of the Labour seats they are targeting in the north-east and north-west. The absence of any more information has let Labour claim that the Tories plan to take it off almost everybody.

Yet the biggest manifesto problem is not a lack of detail, but an excess of it. On social care for the elderly, the Tories were initially clear that Mrs May didn’t want a cap on costs. This was a bold policy statement, hitting as it did a traditionally Tory group: better--off pensioners and their families. It was in keeping with the May team’s belief that Tory modernisation must now tackle class, economics, and the party’s deferential attitude to property wealth and inheritance; and that with a 50-point lead among pensioners she could afford to administer some hard truths.

But abandoning the policy in what looks like panic has damaged May’s whole modernisation project. Her retreat will embolden those who dislike her attempt to move the Tories away from their traditional support for business, the better-off and the elderly. It recalls Winston Churchill’s verdict on Suez: ‘I wouldn’t have dared start, but I certainly wouldn’t have dared stop.’ So Mrs May will win, but her reputation has taken a hit. Revealingly, the Tories have felt obliged to stop using their ‘strong and stable’ mantra about her leadership.

Ultimately, she will prevail because Jeremy Corbyn is fundamentally unelectable — not because she herself proved an inspired strategist. This matters because of her relationship with her cabinet and her party. She has been very good at observing the propriety of cabinet government, but long before she called the election, cabinet members had begun to grumble that the more meaningless the decision, the more they were consulted, and vice-versa. The election has compounded that feeling, as ministers realise how peripheral they are. Even some of those most involved in the campaign were taken aback by manifesto policies. If Mrs May does run into trouble, there will be no stampede of ministers rushing to defend her.

The Prime Minister joined the party as a teenager, met her husband at a Tory disco and still goes out canvassing most weekends. Party members saw her as someone who shared their values and was much closer to them, both politically and socially, than Cameron and Osborne. But to hear even Tories talking about the ‘dementia tax’ is to realise that many members are now wondering if she really does share their worldview.

One of those closest to her observes that before this campaign, May was a blank canvas on to which voters could project their ideal leader. Crucially, they were determined to give her the benefit of the doubt. If she was uneasy on TV it was because she was a serious politician, not a slick salesman like Cameron or Blair. If she didn’t say much, she was keeping her cards close to her chest and didn’t feel the need to say something about everything. The campaign, though, has given May more definition — and in doing so cost her support. By seeking to consummate the marriage, she has ended the honeymoon. The Tory campaign appears to have acknowledged this. In recent days the focus on Mrs May to the near-exclusion of all else has been replaced by a broader-based effort.

May has one of the most essential qualities for any successful politician: luck. There is every chance that she won’t face any better opposition in the next parliament than she has in this one. Jeremy Corbyn might do well enough to justify hanging on as Labour leader. Many party moderates had privately hoped that a thumping defeat would sober up the membership and facilitate Corbyn’s removal. Now it looks like he might increase Labour’s vote share, even while losing heavily. His supporters would then insist that he deserves more time; that Labour’s progress in the campaign proved that when the country saw Corbyn unmediated, they liked him.

Until two years ago, nearly everyone in the party would have considered him too left-wing to be leader, let alone prime minister. Indeed, most of his MPs signed a motion of no confidence in him. Many hoped he’d fall flat on his face in this election, paving the way for a leadership contest: the idea that voters want a far-left Labour party would have been tested to destruction. If Corbyn emerges with a greater vote-share than Ed Miliband achieved, it will make him far harder to depose.

In some ways, Corbyn is pulling off Miliband’s ‘35 per cent’ strategy — adding Greens, left-wing Liberal Democrats and some Ukip voters to the Labour coalition. The problem is that with Ukip’s collapse and the shift back to two-party politics, pulling together 35 per cent of the vote doesn’t put you in power.

Any prospect of an alternative opposition to Labour emerging has been dashed. The Liberal Democrats seem to have had a worse campaign than Labour. They had a plausible strategy: to pose as the tribunes of the 48 per cent who voted Remain. Even if you consider that half of those who had opposed Brexit are now reconciled to the result, this still gave them a chance to advance on the mere 8 per cent of the vote they won last time.

But their campaign has failed to launch. Tim Farron, their leader, has made no impact at all. Even in the minor parties’ debate, he struggled to stand out. There is a sense that the only real cause of Lib Dem concern for the Tories is now in Twickenham, and that’s more because of Vince Cable’s personal brand in his old seat than any Lib Dem revival. This is quite a turnaround from the start of the campaign, when a dozen Tory MPs in Lib Dem target seats met Mrs May to plead for extra resources to save their bacon.

Ukip, meanwhile, has collapsed. The party is struggling to come up with a reason to exist now that the country has voted to leave the European Union. A large part of its vote has simply moved to the Tories — the polls suggest a third, but ministers are convinced that it is more than half. As the Tory part of Ukip’s support goes home, some of its Labour-inclined voters are doing the same. Even the optimists in the party accept that they haven’t much chance of winning a seat in parliament this time round. Combine that with them losing their MEPs in 2019, and it is hard to see how the party can keep going with no base in local government, Westminster or Europe. Ukip’s problem is compounded by the fact that its leader Paul Nuttall has few of Nigel Farage’s skills. His declaration that he would be happy to personally put child killers and terrorists to death made him sound like he’d was applying to be Lord High Executioner, not prime minister.

All of Theresa May’s troubles are relative. If in 2015 you had offered David Cameron even the lowest of the poll leads that Theresa May has enjoyed during this campaign, he’d have bitten your arm off. Very few prime ministers run for re-election sure of their safe return to Downing Street.

But the initial hopes of a 1983-style triumph, one that established their leader as the defining political figure of the age, look set to be disappointed. Instead, May’s victory will be more like Margaret Thatcher’s 1987 landslide. She won, and won big, but the campaign wobbles along the way destroyed for good her aura of invincibility.

Spectator.co.uk/PODCAST

She will prevail because Jeremy Corbyn is unelectable - not because she has proved an inspired strategist

James Forsyth and Tim Shipman of the Sunday Times on the campaign shambles