She did lose because she moved a little bit left and the voters did not show up.

We’re saying you don’t understand cause and effect.

You are saying A (moving left) caused B (losing).

If A didn’t happen, then B also would not have happened. Therefore, “if she had stayed to the right, she would have won.”

Edit: I think I figured out what I’ve got wrong. If I rephrase what you said, then it makes more sense:

“She did lose because the voters did not show up, even though she moved a little left.”