The Polls Have Shifted Toward Harris. Is It Real, or Something Else?

Last week’s New York Times/Siena College polls showing Vice President Kamala Harris leading in three swing states led some Republicans and Democrats to ask the same question: Is this real?

At the center of this question is whether the Times/Siena polls have enough voters who supported Donald J. Trump in 2020. The Trump campaign released a memo arguing that our polls would have actually showed a Trump lead if we had weighted the results properly.

The Trump campaign’s critique focused on something pollsters refer to as “recalled vote.” In the polls of Pennsylvania, Michigan and Wisconsin, respondents recalled backing President Biden over Mr. Trump by six points, 52 percent to 46 percent, even though Mr. Biden actually won these three states by an average of about 1.5 points. The Trump campaign used this data point to say Mr. Trump would have led if the poll had the “right” number of Trump 2020 supporters.

This isn’t an absurd argument. In recent years, many pollsters have embraced recalled vote in exactly the way the Trump campaign describes: as an accurate measure of how people voted in the last election, which can then be used to evaluate the partisan balance of the sample. As an idea, it makes logical sense.

But over the longer run, recalled vote hasn’t usually been very reliable. Oddly enough, this is one of the first things I remember learning when I started getting interested in polling methodology in the fall of 2004. Back then, it was George W. Bush who led the polls, and it was the Democrats trying to prove that the polls were skewed. Among other things, they argued the polls had too many Bush ’00 voters, based on recalled vote.

A CBS News/Times poll at the time, for instance, found Mr. Bush and John Kerry tied, but