The early reports from the ground in New Hampshire indicate a massive voter turnout, likely a record, particularly on the Republican side. According to exit polling data, undeclared voters (which make up the largest bloc of New Hampshire voters) were a higher percentage of the Democrat vote than the Republican vote, although the Republican vote is expected to be higher overall:
It's difficult to read too much into these tea leaves, but this may be an indication that Trump is about to underperform relative to his polls again. Granted, Trump could underperform by quite a lot and still win New Hampshire. Also, it at least possibly indicates some weakness for Kasich. Definitely it spells doom for Hillary Clinton.
The indications also are that more than half the Republican field made up their minds in the last 48 hours - another bad sign for Trump (and possibly also Rubio).
These are the bread crumbs we have to read.