When you do it, try to address the larger underlying problems, not just the problems with Trump. Otherwise, there's a good chance they'll just move over to some other bad candidate, like Ben Carson.
A lot of Republicans have too low a view of the Republican leadership and too high a view of the American people, for example. They don't know much about electability. They think voters are more conservative than they actually are, and they underestimate how much physical appearance, communication skills, reputation, and other such factors determine how people vote. Something that needs to be emphasized is that we don't vote alone. We vote with other people, and those other people limit our options. At this stage in history, the corruption of the American people limits our options much more than some Republicans realize or want to admit.