The real reason why the party is failing was already stated: The grassroots Republicans dislike the 'liberalism' of current Republican congressmen and governors, and trust even less the leadership ability of the GOP machine.
You got it. To make it even worse is that both wings see the leadership as being there opposites politically. Moderates see the leadership as being too conservative, while conservatives see them as sellouts. Sometimes the agree on the reasons like lack of competence, over spending, corruption, others they disagree. The problem is we are running moderates and unless they start winning, conservatives are just going to say why bother to run them then and support there own candidates in those cases. You can't argue that we haven't run moderates. The truth is that until the moderates shut up about the platform, they will continue to scare the sh**t out of the social conservatives, the purging will continue.