When O’Reilly’s day has passed, though, he certainly will have left a lasting stamp on cable news, which is increasingly a medium of outsize, super-opinionated franchise personalities. It is hard to remember, without taking a minute to think about it, who delivers the morning and evening news on the cable networks, or who the main reporters are. Cable is not a medium for providing information, and it is not going to become one anytime soon. Cable is the world that Bill O’Reilly made. National politics will change long before that does.