This may be an apt analogy. If you want to serve ice cream at home to guests, you usually stock up on vanilla because its acceptable to everyone.
A national political candidate has to hit that balance where he/she is acceptable to both conservatives and moderates in order to win.
We all oppose radical Islamists simply because they are too radical to bring into our social compact. The same principle holds true in politics. Winners are never from the extremes unless they hide their true self like Obama was able to do.
If Cruz is too extreme for republicans, then it looks like we need to start our own party.
Bold colors, not pale pastels.