The 2014 election cycle had a number of seats that were considered competitive. Of these races, only two ended up with a Democratic victory, and New Hampshire was one of these. The race was between Jeanne Shaheen, the one term incumbent, and Scott Brown, who had previously been the Senator from Massachusetts.
For many decades, New Hampshire had been a solidly Republican state, although it was never a very conservative state, instead being a "Rockefeller Republican" state, fiscally conservative but with a highly educated population that was resistant to the rise of religious conservatism. When Shaheen supplanted John Sununu in 2008, she took one of the last remaining old-style Republicans out of the Senate. It seemed that New Hampshire had switched into following the political patterns of its more liberal New England neighbors. This was especially the case when, despite speculation about it being a swing state in the 2012 election, Obama won it by six points.
Shaheen also seemed to be a strong candidate, well suited for her state. Scott Brown had been a senator in Massachusetts for two years, but he won that position during a special election, and he had recently been defeated for reelection. He then moved to New Hampshire for the specific purpose of seeking office, something that is looked at as slightly ill-mannered. Although there have been people who have held elected office in multiple states, no one has done it since the 19th century. Scott Brown had an uphill battle.
The election came much closer than the polling or commentary predicted, with Shaheen winning by a three point margin, a result that wasn't settled until late in the night.
The election could be seen in two different ways. On one hand, it shows that although one of the Democratic Parties key demographics is college educated voters in the Northeast, that this demographic is hardly one they can take for granted. This race, together with a number of other contests in New England, showed that there the strain of conservativism still exists in New England. On the other hand, the fact that Shaheen managed to win, even in an election cycle that was unfavorable to her, and in a state that was traditionally Republican, shows that New Hampshire may have settled into being a basically Democratic state. The other result of the election is that Scott Brown, who has ran for senator three times in five years, and won only once, is probably going to retire from seeking national office.