The border counties with the most Massachusetts refugees are deep red.
It’s the Vermont border counties, filled with New Yorkers who for some reason couldn’t settle down in a socialist paradise and crossed the Connecticut River to live in NH that are the deep blue areas.
The Bluest areas of NH are around the major colleges. Hanover, Durham/Portsmouth, Plymouth, Keene. Lots of liberal college employees and rich kids.
The other major area are the wealthy people who retire to their lakefront houses. Many of these people spent the majority of their life in MA, RI, CT, NY and came to NH on the weekends in the summer. Now, they live year round at the lake house. They pay huge property taxes and are living off their investments. Except, now they get to vote here because they are full time residents.
The other strong Dem area is Concord. The state of NH employees tend to be more Dems than Rep.