Cain was actually 3rd in this pre-Ames poll at 10%. Notice, in this screenshot, who Schieffer's "Face the Nation" didn't include:
When Bob Schieffer and CBS decided to exert editorial control over their “reporting” the actual facts of The Des Moines Register’s poll, they ceased to be journalists and crossed the bright line into being propagandists, into shaping and controlling the news.
That must be why Schieffer said Cain can ‘no longer be ignored’. He’s admitting he tried to ignore him, but Cain thwarted Schieffer’s plans.