The Northeastern suburbs were the first suburbs to fall to the Dems after Reagan's presidency. Much like how Eisenhower's winning the South was a precursor to the Southern realignment that would occur in 1980-present, Clinton's winning the Northeastern suburbs in 1992 was the canary in the coal mine for the suburban realignment we're witnessing today.
It's all about those Boston suburbs/exurbs.
... Weren't the Boston exurbs the most Republican part of New Hampshire, like, right up until 2016? And even in 2016, they were more Republican than the state as a whole...?
They still moved rapidly. Bush won Hillsborugh by 32 points in 2008, he won it by 2 in 1992 and Clinton won by 8 in 1996.