senior advisor to mitt romney s campaign and scott walker ending his presidential campaign amid poor poll numbers and lackluster showings in the presidential debates. we re also following the backlash against another republican candidate, dr. ben carson, pafacing calls to drop t after saying he doesn t think a muslim should be president of the united states. let s bring back dana bash. what s the latest on dr. carson? i think i can answer that by looking back to 14 years ago, right after 9/11. you remember george w. bush, republican president made very passion net statement appealing for tolerance in this country when it came to muslims. hard to believe how different the republican conversation is now. even in a campaign full of explosive comments, this one immediately stood out. i would not advocate that we put a muslim in charge of this nation. i absolutely would not agree with that.