I don’t think it is impossible but they need help.
Michigan, TCU, LSU dropping games would shoot them back up into top 6. USC dropping a game to ensure no 1 loss PAC12 champ means Clemson goes up into Top 5.
Of course the question then is how do you put Clemson ahead of 2 Loss Bama if they were initially behind a 2 loss Bama for multiple weeks