The polls have shown Donald J. Trump with an edge for eight straight months, but there’s one big flashing warning sign suggesting that his advantage might not be quite as stable as it looks.

That warning sign: His narrow lead is built on gains among voters who aren’t paying close attention to politics, who don’t follow traditional news and who don’t regularly vote.

To an extent that hasn’t been true in New York Times/Siena College polling in the last eight years, disengaged voters are driving the overall polling results and the story line about the election.

President Biden has actually led the last three Times/Siena national polls among those who voted in the 2020 election, even as he has trailed among registered voters overall. And looking back over the last few years, almost all of Mr. Trump’s gains have come from these less engaged voters.

Importantly, these disengaged low-turnout voters are often from predominantly Democratic constituencies. Many continue to identify as Democratic-leaning and still back Democratic candidates for U.S. Senate, but they nonetheless are backing away from Mr. Biden in startling numbers. In our polling, Mr. Biden wins just three-quarters of Democratic-leaning voters who didn’t vote in the 2022 midterm election, even as almost all high-turnout Democratic-leaners continue to support him.