'One thing about this US election, it is probably going to be unbelievably close'

If you know one thing about this US election, it is probably that it is unbelievably close, right? On a knife edge. Neck and neck.

I’ve long worried about the extent to which the polls impact our coverage of all modern elections.

We’re obsessed by the narrative of the horse race; who is ahead, who is closing on the rails, who has late momentum. And above all, who is going to win.

It is human nature, I suppose, to want to know the outcome of a race before it is over, especially when everyone is agreed that so much is at stake. But the basic truth about this election is we have no idea what is happening out there.

Most reputable experts have grown increasingly concerned about the way pollsters have "herded" towards predicting a tie.

They were four points wrong in 2016 and the same again in 2020 and there is no good reason to suppose this time will be any different.

All of which is why a new Iowa poll has comprehensively put the cat amongst the pigeons.

That is because the firm involved has a much better track record than most (it has got both the last two presidential elections pretty much bang on in Iowa) but also because of the shock result.

It has predicted that Kamala Harris is going to win by three points a deep red state that Donald Trump won by eight last time.

If that is right, it would be seismic in itself, but the underlying data seems to suggest that women – older women in particular – are breaking late for Harris in very big numbers, primarily motivated by the issue of abortion.

Iowa introduced a six-week abortion ban in July that has proved very controversial and provoked round the clock coverage on local media.

So the number one topic of discussion here in Washington as we go into the big night is whether pollsters, terrified of underestimating Trump’s support as they did in the last two elections, have over-corrected on that front and missed a big surge in female voters coming out in large numbers to send a clear message on the issue of reproductive rights.

Or to put it another way, if this Iowa poll is right then we may well not be waiting until Saturday (as we did last time) for the result.

On these numbers, Harris would probably win Ohio as well (another red state in recent cycles) and sweep the blue wall in the mid-west – and perhaps other swing states as well.

It is even conceivable that Texas (which also has tough abortion laws) and even Florida might be in play. But to recap, we don’t know. We just can’t.

So do join us for our all-night election special. As each set of polls close, we will be crunching the data to search for any early signs of which way the wind is blowing.

Is that Iowa poll right? Are women going to win this for Harris? Or has Trump once again defied the odds?

Join Tom Bradby for the ITV News US presidential election special, Harris v Trump: The Results, with in-depth analysis from 10.45pm on ITV1 and ITVX

Want an expert briefing on US politics and the presidential race? Listen to our latest podcast Talking Politics USA