Joe Biden’s lead has evaporated in four key swing states, according to a polling average released by RealClearPolitics.
In Iowa, Georgia, North Carolina and Ohio Donald Trump has seized the lead, the site claimed - although several polling experts said that the results were not credible.
RealClearPolitics still gave Mr Biden a 7.2 per cent lead nationally, with a 0.09 per cent lead in Arizona and Florida, and a 1.2 per cent lead in Pennsylvania.
The biggest collapse of support for the 77-year-old was in Iowa, where as recently as Friday he was ahead according to RealClearPolitics’ average by 1.2 per cent.
Mr Trump now leads Iowa by 2 per cent of the vote; Georgia by 1 per cent; North Carolina by 0.2 per cent; and Ohio by 1.4 per cent.
Mr Biden previously led polling in all four states, but saw his advantage dwindle in recent days.
Polling experts cautioned, however, that RealClearPolitics’ survey was not giving a balanced view.
Their average was heavily weighted by polling data from Trafalgar Group - in particular in Georgia and Ohio.
The Georgia-based polling firm weights its surveys for “social desirability bias,” taking into account the idea that some Trump voters are afraid to be honest with pollsters.
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That methodology has included asking respondents who they believed their neighbours planned to vote for, as well as differences in how the company Trafalgar judges who is most likely to vote.
The firm was, however, one of the only polling firms to correctly predict Mr Trump would win Michigan and Pennsylvania in 2016.
Trafalgar’s last surveys leading up to this week’s election suggested Mr Trump is leading Mr Biden by 5 per cent of the vote in both Ohio and Georgia, making their polls a strong outlier.
Nate Cohn, the New York Times’ polling expert, described RealClearPolitics as “a small casualty of this election”, and said they were no longer credible.
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A second polling expert said they were unabashedly pro-Republican.
“They've been doing this all year. Arbitrary date ranges and arbitrary exclusion of some polls, even within range, which just happen to be unfavorable to the GOP,” he said.
One small casualty of this election: the RealClearPolitics average. It's never been perfect, but I've cited it in the past as a simple no-questions-asked average. Unfortunately, that's not possible anymore.
— Nate Cohn (@Nate_Cohn) November 3, 2020
I hope after this election we can stop pretending RealClearPolitics is anything but the Rasmussen of aggregators.
They've been doing this all year. Arbitrary date ranges and arbitrary exclusion of some polls, even within range, which just happen to be unfavorable to the GOP. pic.twitter.com/4ybChdm0uq
— Damon 🗳 (@DamonMag) November 2, 2020