Nate Cohen on the Times poll.
That said, it would not be hard to explain if Vice President Harris support really has faded a bit in recent weeks. After all, she was benefiting from an ideal news environment: an uninterrupted month of glowing coverage from President Biden departure from the race in July to the Democratic convention in August. It is possible she was riding a political sugar high, if so, it would make sense if she came off those highs in the two uneventful weeks since the convention.
There is also a plausible reason the Times/Siena poll would be the first to capture a shift back toward Mr. Trump, There simply have not been many high quality surveys fielded since the convention, when Ms. Harris was riding high. There was a scattering of online polls this week, but there has no been a traditional high quality survey with interviews conducted after Aug. 28.