AI is -- at least in part -- a popularity contest. Excluding the teeny-bopper factor, Sanjaya stayed in longer than he should have because people liked him. Norman/Nick is the same way. People like him and will want to keep him around for a while, even though he's not nearly talented enough to warrant it. Tatiana is a different story. The judges kept her in because the scary vortex of drama she creates is interesting t.v., but she won't get votes. Remember that bitch Brenna from Season 4 or 5? Viewers couldn't stand her. She got the boot after two weeks of semi-finals.