I'm sure someone will be along to explain it in full detail soon enough, but here is a synopsis:Jase in season 5 was constantly on the nomination block.
In the subsequent Power of Veto competitions, he won and took himself off the block.
When Nakomis was Head of Household she came up with a foolproof plan to keep him on the block for the vote: Backdoor him!
1. Put 2 people up on the block that she trusted. Neither of which were Jase, of course.
2. In that season, the HoH and the nominees picked the other three participants in the Power of Veto challenge, Jase wasn't picked to participate, of course, and more of the three players' allies were picked. (He might have been made host, but I'm not sure.....)
3. Once a winner was determined, one of the nominees are vetoed out and Jase put up in their place.
4. Voting takes Jase out soon after.
Because 3 Vinces are better than one.