Why are we placing so much faith in opinion polls? Let's be honest, they've let us down, badly, time and again in recent years. The firms behind the polls insist they've fixed the flaws that scuppered their attempts to predict the 2015 result, and the clear trend from all the surveys is of a tightening race, with Labour gaining ground on the Conservatives.
But is that what will happen on Thursday? Labour's poll rating may be improving, but that doesn't mean they're about to take us into a hung parliament.
The fear of many inside Labour is that they're just racking up thousands more votes in seats they were already going to win. Usually loyal Labour voters, reluctant at the start of the campaign to back Mr Corbyn, have been won round. But this could simply increase majorities in the party's London fortress, and in Wales where its fortunes have also recovered.
Labour already holds close to two-thirds of the seats in London and Wales. There are few potential gains there. As the campaign comes to an end, the truth remains as it was on day one. This election will be won and lost in the North of England and the Midlands.
That's why Theresa May has spent so long visiting Labour seats in both regions, with a hard Brexit message targeted at former UKIP voters.
As that party fades into obscurity, millions of votes are up for grabs. Many from former Labour supporters. Could they really be tempted to cross over to the Conservatives? For many communities in the North, the Tory brand is toxic. That's why Theresa May's surgically removed it from posters and banners.
It's been claimed more than half of defecting UKIP voters are now backing the Tories. Labour campaigners say they've won some of them back during this campaign -- but even they admit it won't be enough to stop the loss of vital seats across the North and Midlands.
There are 46 Labour-held seats across both regions where the UKIP vote in 2015 exceeded the winning majority. In 24 of them, the UKIP vote was at least double Labour's majority. They're the seats the Conservatives are desperate to win on Thursday -- and despite the narrowing national polls, they remain confident of pulling off a few surprises.
It's clear that Jeremy Corbyn has had a good campaign, far exceeding many people's expectations including many in his own team. Theresa May has performed less well, stilted and wooden. But, asked who they prefer as Prime Minister, voters still seem to back her over him.
Mrs May's been damaged by this election campaign, and even if she wins a majority of 50 or more her image has taken a knock. Mr Corbyn has proved himself more popular on the doorstep than he ever was with his own MPs. They'll struggle to depose him, even if he returns with two dozen fewer MPs.
Despite the narrowing gap, that remains the inescapable conclusion of the electoral mathematics. Then again, such predictions haven't gone terribly well lately...