If the yesterday's episode proves to be true and Michelle votes out Jordan and Natalie votes out Jeff, then Kevin has the deciding vote. If Kevin actually listens to Michelle and keeps Jeff, he would be making the worst decision of the game.
Not only would Jeff be gunning for Kevin but Jeff is by far the strongest threat left in this game. Jeff could easily win the game against any of the people left(depending on if people like Jordan and Michelle get put on the jury). Kevin would be fucking himself over big time.
Although Jordan would be gunning for Kevin too, she isn't a threat at all. You want to have the lesser of 2 evils in this instance.