I think Trump has tapped into something among about a quarter of Republican voters. But it hasn't spread beyond that, not yet anyway. I come to that conclusion by looking at favorable/unfavorable numbers among the voters. Nationally Trump has 36% favorable rating vs. 59% unfavorable.
http://i2.cdn.turner.com/cnn/2015/im...-.gop.2016.pdfThat at this point in time doesn't bode well for the general. Among Republican voters Trump has a 68% favorable rating vs. 29% unfavorable. Democrats view Trump with a 16% favorable 80% unfavorable and probably the most important group if Trump is to win the white house is independents. Due to the smaller base, the Republican candidate must win around 54% of this group. But Independents and independents only give Trump a 33% favorable rating vs. 61% unfavorable. So unless Trump can change the views of the independent voter, he will not win the white house.
But there is plenty of time for that to happen, but it is hard to get people to change their minds once they made them up. Trump has very little room to grow or improve. A lot of candidate do not approach the 90% or so that say they know enough about him or her to give the pollsters an opinion. Hillary Clinton is the only other candidate so far that matches Trump real close in the favorable/unfavorable ratings. Independents at as of today do not like either.