Kamala Harris and Donald Trump are now even in polling averages, with Harris’s previous lead over the Republican candidate narrowing three weeks before election day.

Harris previously commanded a sizeable but not an election-winning 4.3 per cent lead in national polling averages, which has decreased to about 2.7 per cent.

David Smith, an associate professor at the Centre for American Studies, said the narrowing of polling could be attributed to several factors.

“As we get closer to election day, fewer and fewer people are undecided and it may be the case that Republicans who have felt reluctant about Trump are nonetheless biting the bullet and deciding to vote for him,” he said.

“The narrowing has been small and you could also take into account that when Harris’s national polling lead was at its peak, it was at a time when Democrats felt particularly excited about her replacing Biden.”

Methodology

Election polling in 2020 produced results that, on average, were far different from Joe Biden and Trump’s final results, with experts labelling it an “error of unusual magnitude”.

Joe Biden commanded an average polling lead of 8.4 per cent against Trump in 2020, but won the election with a margin of 4.5 per cent. Photo: Getty

Kim Strassel, a conservative American political commentator, said that although the Trump campaign is suggesting it was seizing the advantage before election day, that remains to be seen.

“Look at 2016 and 2020, where he was well behind the Democrats and those cycles and still either won or almost won – just barely lost – and this time he’s looking much better,” she said on the Potomac Watch podcast.

“There’s a possibility the polls are getting it more right this time, and that what we have is truly a race that is on the knife’s edge in every one of these swing states.”

In key swing states, the polling between the two candidates is even more deadlocked, with Arizona, Georgia, Pennsylvania, Michigan, Nevada, North Carolina and Wisconsin all recording less than a two per cent margin.

Smith said that because of the inaccuracy of polling in 2016 and 2020, many reputable pollsters have changed their methodology.

“A lot, but not all, of pollsters are using what is called weighted recall average, which means they ask voters who they voted for in 2020 and weigh the sample to try to make it look more like how votes were distributed at the last election,“ he said.

“According to Nate Cohn at the New York Times, around two-thirds of pollsters are doing this and it may also account for the closeness and stability of the results.”

Knife’s edge

The last time a Democratic nominee was under-represented in polling was Barack Obama’s 2012 win, according to Smith.

Smith said that although Harris’s vote may be underestimated, there is a high likelihood that the election is decided by a small margin of voters in key states.

“Last time around, it was widely calculated that 44,000 voters made the difference. We’re talking about 11,000 in Georgia, 10,000 in Arizona and just over 20,000 in Wisconsin,” he said.

“One of the critical things we saw last time was that the margins were narrow, but big enough that no legal challenge was going to overturn them.

“If it’s fewer than 1000 votes, then you start to get into the territory where it’s more likely that you get legal challenges from both sides.”