http://en.wikipedia.org/wiki/No_true_Scotsman
Imagine Hamish McDonald, a Scotsman, sitting down with his Glasgow Morning Herald and seeing an article about how the "Brighton Sex Maniac Strikes Again." Hamish is shocked and declares that "No Scotsman would do such a thing." The next day he sits down to read his Glasgow Morning Herald again and this time finds an article about an Aberdeen man whose brutal actions make the Brighton sex maniac seem almost gentlemanly. This fact shows that Hamish was wrong in his opinion but is he going to admit this? Not likely. This time he says, "No true Scotsman would do such a thing."
Apparently "No True Conservative" could possibly be rejected and repudiated by American voters, so the only answer is to be more conservative or right wing.
The only answer to why they have been forsaken by voters is because they strayed from the True Path of the Right Winger. Not that they have become too right wing.