There isn't any one group, that has enough people, to provide a Republican (or Dem) win by itself.
Even a lot of Dems voted for Bush, because of national security, of have you forgotten Ed Koch. He was not alone.
The way for the Republicans to win is exactly the way Bush and Arnold says, you have to appeal to the spectrum from the right, to the middle.
Where do you think Bush's compassionate conservatism comes from, except understanding the realities, which some people here unfortunately refuse to grasp. ( Note I didn't say people couldn't grasp it, they just don't want to, preferring to live in a fantasy world.)
And now you say, "There isn't any one group, that has enough people, to provide a Republican (or Dem) win by itself."
In other words, you misrepresented the true political landscape in your first post.
Setting that aside, it doesn't necessarily follow that moving left is the way to capture more votes. I hear that assertion made often, yet I've yet to see evidence to back it up.