'Closer than a coin flip': US polling guru reveals his final US election ...

Famous statistician Nate Silver has published his final US election forecast modelling, and concluded the outcome is "literally closer than a coin flip".

Silver uses statistical analysis to crunch poll data on the website FiveThirtyEight and famously called the outcome of the 2012 election correctly.

This year he ran 80,000 Electoral College simulations of the contest between Vice President Kamala Harris and former president Donald Trump.

Harris won 40,012 of those simulations, while Trump notched up 39,988 victories.

"The race is literally closer than a coin flip: empirically, heads wins 50.5 per cent of the time, more than Harris's 50.015 per cent," Silver wrote on his Substack page on Tuesday (Wednesday AEDT).

Silver said that Harris did not emerge as the victor in 39,988 simulations, and of those, 39,718 were outright victories for Trump.

The remaining 270 simulations resulted in an Electoral College tie, Silver said, adding that would lead to a Trump victory through voting in the US House of Representatives.

"This is my fifth presidential election – and my ninth general election overall, counting midterms – and there has never been anything like this," Silver wrote.

Silver's prediction comes just days after a poll from the Des Moines Register and Mediacom in Iowa found Harris leading Trump in the state, with 47 per cent to 44 per cent.

That margin falls within the poll's 3.4-point margin of sampling error and suggests no clear leader in the state, which has widely been rated as solidly in the Republican column during this year's campaign.

The findings suggest a shift toward Harris compared with the previous Iowa Poll, in September, which found a narrow edge for Trump.

Iowa has a mixed record in the last four presidential elections, breaking for Barack Obama in both 2008 and 2012, while Trump won it in 2016 and again in 2020.