It looks as though Republicans have very little effect on national approval trends. In terms of approval for Trump, a 24% rise in Republican approval pans out to a 3% national rise.
In June of 2015 44% of Republicans favored Donald Trump compared to 32% of all Americans. This month 68% of Republicans approve of Trump, a rise of 24%. But, only 35% of all Americans favor him, a rise of only 3%.
Using this ratio, the good news for Trump supporters is that the #nevertrump folks will have minimal impact on the election. If it takes 8 Republicans to move general sentiment up 1 tick, the 32% of Republicans opposing Trump probably only account for 4% of the general unfavorable rate.
The bad news may be that Republicans as a whole don't matter that much.
H/T Harry Enten