Reuters has an interesting article on how Trump is failing to fire up the conservative base. I the think the problem is actually deeper than that.
Here is one of the charts they use to illustrate their point:
Their main point is that Trump is down 20 points (61.5%-82.6%) with moderately conservative voters, compared to Romney in 2012. What i find striking is that he is also down by 10 points (74.1%-83.9%) with Very Conservative men as well. This may mean that if Trump finds a way to win over the moderates, he may very well further alienate the die-hards. So he’s down 10 now with the far right, and he moves to the middle on some issues, which he may have already started to do over this past weekend, then he improves his standing with the moderates, but he looses ground with the far-right doctrinaires.