Is NH still a swing state?

[Badger]

NH can be won by a Republican, but it is growing increasingly difficult and will soon be impossible.  The Vermontification is well under way.

This hits the nail on the head. I won't go so far as to place New Hampshire in the "Safe D" column, but it definitely leans left: no state that reelected its Democratic governor and Democratic Senator in 2014 can be counted a true toss-up.

Ohio, Virginia, Florida, Iowa, New Mexico, Colorado, and Nevada haven't voted Republican in eight years. Are they solid Democratic states too?

New Mexico really isn't a swing state at this point, and while Virginia could still vote Republican in the near future, it probably tilts D in presidential races. The remainder of those states either elected a Republican Senator in 2014 (Iowa, Colorado) or re-elected a Republican governor that same year (Ohio, Florida, Nevada). Simply put, there are recent examples of Republicans winning statewide races in those states; the last Republican to do so in New Hampshire was Ayotte in 2010. Like Violent Socialist said, it's still possible for the GOP to win there, but it's hardly of the same stripe as Ohio and Colorado.

Pennsylvania and Michigan haven't voted Republican since 1988. Wisconsin hasn't since 1984. Minnesota hasn't voted Republican since 1972.

Yes, and there is no reason to believe this trends is in danger of ending. The fact that the GOP won elections in Wisconsin and Michigan in the wave years of 2010 and 2014 does not make them legitimate swing states any more than Donnelly's 2012 victory makes Indiana a swing state. A down-ballot Republican can still win here under the right circumstances, but they will continue to vote Democratic at the presidential level for the foreseeable future.

Other than adding Nevada really isn't a swing state at the presidential level either, this is the correct answer.