My friend Mardis has a post wondering why a grown up Republican does not challenge King. I gave a brief response at The Pocket Mardis but I want to speak about it a little further.
The reason no Republican will challenge King is because they all agree with him. The Republican base is fueled by a toxic brew of of hatred, resentments, and fears. There is a darkness in the soul of the modern GOP's base, and King speaks to and for the darkness. In short, Republicans keep electing Steve King because he is one of them.