Even with the Broncos' overtime win over the Bengals Monday night, Denver's lead in the AFC West is not safe. Should they lose to the Chargers in the season finale and the Chiefs beat the Raiders, the Chiefs would steal the AFC West crown right off of their heads.
A major reason the Broncos are in danger of losing the AFC West right now is because the Raiders beat them two weeks ago. So, essentially the Raiders made it so both the Broncos and the Chiefs would be fighting for the division crown.