A little voter registration data helps ‘splain this.
In 2020, Ds had an 87,000 lead in NH.
Today? Rs with a 44,000 lead.
Party Registration History 1970-2024
In late 2023 R's had taken an extremely slight lead in registrations over Democrats (with, as always, "Independents" having a greater number than either party).
Then suddenly in 2024, Democrat total has dropped, Independent total has dropped, Republican total has skyrocketed. Seems like the kind of "gift horse" whose mouth shouldn't be too closely examined. In NH, party registration AND how people vote, fluctuate all over the place. One year they look like they might be going back "red" and the next year they go lurching to the left. There is no consistent pattern and hasn't been one for many, many years.
Four years ago, the polls were way off. The biggest single reason was over-sampling of Ds. The polls, on average, had a skew of 4 points D. Based on a variety of information, including trends in voter registration, I thought the Ds would have a skew of 2 points. It turned out, via the Exit Poll, the Ds only had a 1 point edge. I am seeing a similar thing this year. Rs continue to gain in registration, but this isn’t being reflected in the partisan composition of the polls. I suspect we will again over-perform the polls.