"in New Hampshire" is the important caveat here, and this is an outlier-low for Trump poll too. nationally she continues to poll anywhere from 30 to 50 points behind him, and in any case it's not a given that "winning New Hampshire" is capable of catapulting her to victory with a Republican electorate that clearly likes Trump a lot
At this point there's a huge swath of Republican voters who don't know who the heck she is. Trump may have done the right thing by snubbing the primary debates because he's managed to help keep the knuckle-draggers who form his base ignorant of the other candidates who aren't trying to out-Trump Trump himself.