ROCKFORD, Ill. — The front line of this year’s fierce fight for control of the U.S. House of Representatives cuts straight through the river cities and rural communities of the 17th Congressional District in northwestern Illinois. But on the streets of Rockford and Rock Island, the face-off for the open seat between Democrat Eric Sorensen and Republican Esther Joy King is being met by voters with stony silence. The low-key nature of the high-stakes contest playing out in their towns comes despite the fact that national politicians are paying close attention to the election, which is considered…