What is a “primary voter”? I don’t recall other polls using that term. Likely, registered etc but not “primary”.
From article (curious weighting):
Another possible explanation for Trump’s decline in the new NBC/WSJ poll is an increase in “very conservative” Republican voters from January’s sample.
If the current poll is re-weighted to reflect the ideological composition from last month, the GOP horserace numbers are: Trump 26 percent, Cruz 25 percent, Rubio 18 percent and Kasich 13 percent — so Trump is ahead by one point, but still down from January.
A primary voter is someone who has an established track record of consistently showing up to vote in a primary election.
Let them have their fun.
They need it and it's only fair to let them celebrate, knowing what the future brings.