Don't let anybody tell you that they saw this coming.

Not the advisers who crafted the campaigns of the leading parties, not even the expert pollsters. No one was predicting an eight-seat leap for Benjamin Netanyahu's Likud in the final days of the contest.

The first sign of a turnaround in the results was the smile on the face of Mr Netanyahu's spin-doctor, Nir Hefetz, as he walked into the Likud headquarters at 9.30pm.

He was listening to a source at one of the television channels leaking him the exit polls which were due to be broadcast half an hour later.

At that point, the news that Mr Netanyahu's Likud had closed the gap with the Zionist Union was enough.

For the man who has taken a lot of the blame for what was seen as a failing election campaign, it was a rare moment of satisfaction. No one had even dared to imagine that five hours later, with the prime minister's victory speech over and as the last celebrating Likud members departed the convention centre, the actual results would indicate that it was now Likud opening a gap, eventually leading Zionist Union by six seats.

It was a night of two victory speeches as Labour Party and Zionist Union leader Isaac Herzog had also announced that he would be seeking to form a coalition.

But once the full results were known in the morning, Mr Herzog called his opponent and conceded.

"Serving in opposition is the only realistic option for us," he said at the first meeting on Wednesday afternoon of the party's newly elected Knesset members.

The surprise was even greater given the widespread belief that Mr Netanyahu had failed to understand the Likudniks who accepted his security agenda but this time were going to vote on more pressing issues: sky-high food and house prices.

On Monday, 24 hours before voting began, leading pollster Mitchell Barak had declared Mr Netanyahu's campaign his "worst ever".

Even Likud's chief campaign strategist, Aron Shaviv, seemed resigned.

The problem, he said, was that Likud voters had been tempted by a "package deal" - they believed they could vote for a centrist party within a potential right-wing coalition but still get Mr Netanyahu as the prime minister.

Mr Shaviv said: "We have been pushing the point that this won't work. We say: if you don't vote for Likud, you won't get Netanyahu."

The realisation of the danger posed by the centrist parties, combined with a final pre-election poll that put Likud four seats behind Zionist Union, galvanised the party to fight for its life. It also won the election for them.

The message pumped out to Israeli voters in the last-minute media blitz was: you are about to get a government that will leave you at the mercy of the wolves.

In an interview on Monday, Mr Netanyahu said that if re-elected he would not allow the establishment of a Palestinian state now, and that the left's goal of re-entering peace talks in the hope of achieving a two-state solution would result in a threat to security.

"In the current circumstances in the Middle East, any territory that you vacate will be used for an armed Islamist state against us," Mr Netanyahu said. "That's exactly what happened in Lebanon. That's what happened in Gaza. And since the Arab Spring, that's what's going to happen exactly in the West Bank - in Judea and Samaria - if we vacate territory."

As Mr Shaviv said, the Israeli right are security-minded "in their DNA" and, in the last days of his campaign, Mr Netanyahu spoke to their deepest concerns.

That the Likud surge was the result of right-wing voters deciding not to vote for the other smaller, right-leaning parties vindicated Likud's last-minute tactic: only an experienced big-gun such as Mr Netanyahu could address this core anxiety.

Some of Likud's success may be put down to mistakes made by the Zionist Union, who, according to a member of its campaign team, were "cautiously optimistic" at lunchtime on election day.

Most observers agree that the Zionist Union leader, Isaac Herzog, made a major mistake when he agreed to share a potential premiership with Tzipi Livni early in the campaign.

Mr Barak said: "Livni was a drag on the ticket according to my polls… and Herzog looked like he lacked self-confidence when he agreed to share power. He was just about to gain traction - polling at about 20 per cent support early on in the campaign, which is a good start - when he brought in Livni and lost momentum."

It was an error the party sought to undo the day before the election when Ms Livni said she would withdraw from the shared premiership deal.

Experts said the Zionist Union could have extended its lead over Likud if Mr Herzog had presented himself to voters in a more personal way.

Mr Barak said: "His uncle was [Israeli diplomat and politican] Abba Eban - he should have leveraged that. Eban is the best diplomat we had – but we heard nothing about it."

One survey found that few Israelis knew much about Mr Herzog.

"He has not done a good job of introducing himself. This has been some mild-mannered guy going against Superman," said Mr Barak.

Indeed, throughout the campaign, leadership polls consistently showed Mr Herzog at least 20 percentage points behind Mr Netanyahu.

The wider story is that the Israeli electorate is fundamentally split. Around 20 per cent left it until the last minute to decide who to vote for, underlining the instability that has endured since the last election in 2013.

The centrist vote was split between two parties - Kulanu and Yesh Atid - but it was bigger than last time.