Excellent analysis. Add in the human factor, however, and I

Think the likelihood goes down to 10%.

An undefeated major school can’t be kept out. The voters wouldn’t dare. The legitimacy of the whole “system” would be sharply in question.

If ND loses from here on out, it will have been to an unranked or barely ranked team (USC). The Greek Chorus will be heard far and wide: “They haven’t played anybody! OK, maybe they played one somebody and they only won by 7 at home! They didn’t have to play a conference champ!” The voters can do 2 SEC, 1 true ACC, 1 B1G and it will look fine.