libel? let us know what you think. the live chat is underway, ac360.com. also ahead, her challenger, chris coons caught up in a controversy of his own, words he wrote a quarter century ago about being a bearded marxist. those two words are being used against him now, we've checked the record. and sanjay gupta, this little girl battling an unknown killer. tonight kylie's parents continue their desperate search for a diagnosis. >> i feel like a bad parent. why can't i help my kid? >> can't really put it into words. just helpless. [ male announcer ] set down your pencils.