It's good news for Sanders, after a poll from WMUR-TV last week appeared to show his gains flattening. But it's not necessarily great news.
The same polling firm did a survey in March, allowing us to see how things have changed since then.
Clinton dropped 10 points; Sanders gained 36. Elizabeth Warren is no longer included in the survey, and it's fair to assume that Sanders picked up much of the 22 points she had back then. Sanders leads by 21 points among those who describe themselves as "very" liberal, and trails among "somewhat" liberals by about a point. Picking up 10 points from Clinton and 22 from Warren gives you almost the full 36 points Sanders gained. (The margin of error, by the way, is just under 5 percentage points, so that's worth keeping in mind as well.)
As we've seen elsewhere, Clinton's favorability has also dropped since March. The net favorability for the candidates has changed along with the poll results.
Sanders's growth is in part a function of his increased name recognition.
What's more, Clinton's "very favorable" support has dropped, and Sanders's has risen.
All of which is good news for Sanders — assuming that this poll reflects both reality and a continued trend. It's too early to tell that, of course.
And also assuming that the sample used in the poll reflects the demographics of the primary electorate. There are big differences in how younger and older voters view the candidates, for example.
The poll more closely resembles how Democrats break down in Census data than who likely voters might be -- which is very hard to determine this far out anyway. If turnout is heavily older, Sanders wouldn't win.
But, then, the conversation we're having today is: "Sanders might not win New Hampshire" rather than "Sanders has no chance." That doesn't prove that Sanders will be the nominee (he still almost certainly won't be), but it explains why everyone is sending this poll around.