While President Biden claims that the polls underestimated him in 2020 and 2022, 2024 polling shows a race that is slipping away from the president in the biggest shift yet.

Calling into MSNBC’s “Morning Joe,” Mr. Biden said that the polls “were wrong in 2020.”

“They were wrong in 2022 about the red wave. They’re wrong in 2024 and come out with me and watch people react. You make a judgment,” Mr. Biden said.

In 2020, the polls accurately indicated that Mr. Biden led in both the Democratic primary versus Senator Sanders and in the general election against President Trump. 

Furthermore, the polling error in 2020 favored Mr. Biden, meaning the general election surveys overstated his popular support in the general election.

While FiveThirtyEight’s average of polls indicated that Mr. Biden enjoyed a 8.4 point lead over Mr. Trump on Election Day, Mr. Biden defeated Mr. Trump by only 4.5 points in the national popular vote.

In 2022, the polls were historically accurate, with pollsters indicating that Republicans enjoyed a small advantage in generic ballot polling, which asks respondents whether they generally prefer Republicans or Democrats.

FiveThirtyEight’s 2022 generic ballot average showed Republicans leading Democrats by 1.2 points in the generic ballot on Election Day. In the popular vote results, Republicans received 50.6 percent of the total vote in House races, while Democrats received 47.8 percent of the popular vote.

Although past polling bias is not predictive of future polling bias — since 1998 polling has overestimated both Republican and Democratic support at different times — neither Mr. Biden nor the Democrats were underestimated by the polls in either election cycle Mr. Biden referenced.

Mr. Biden’s rejection of the polling data in 2024 comes as most pollsters are recording the biggest shift of support in the 2024 presidential campaign in the wake of the debate. And, it’s a shift away from Mr. Biden.

The Cook Political Report released a new polling average Wednesday showing Trump now leading Mr. Biden 46.9 percent to 44.3 percent.

This represents the biggest shift of the election cycle from the statistical tie between Trump and Mr. Biden at 46.5 and 46.9 percent in the Cook Political Report polling average in late June.

While debate bumps or dips often prove ephemeral in presidential races, the Cook Political Report also indicated that Trump’s chances of winning the key swing states of Pennsylvania, Wisconsin, Arizona, and Georgia have increased in the wake of the debate.

“It’s also clear that Trump’s outside-the-margin leads in states like Arizona, Georgia and Nevada are currently safe, leading us to move all three from Toss Up to Lean Republican,” political analyst Amy Waltyer writes. “That leaves three states in the Toss Up column: Michigan, Pennsylvania and Wisconsin.”

The shift in national polling reported by the Cook Political Report is also reflected in other polling averages maintained by FiveThirtyEight and RealClearPolitics, which have both recorded a shift away from Mr. Biden post-debate.

Whether Mr. Biden is able to close the gap between himself and Trump between now and Election Day remains to be seen, though it’s notable that he’ll likely need to do more than just lead Trump in national polling.

Given the Democrats’ structural disadvantage in the Electoral College, Mr. Biden will likely need to lead Trump by similar margins to his 2020 performance if he wants to recreate the same Electoral College victory, though the final election results will likely depend on the outcomes in just a few swing states.