Mace Windu targeting error

It is hard to explain but unfortunately that is not a bug. Just like how Mace cannot swap turn meter without first selecting a target, JMK cannot cleanse himself without first being targeted. This is different from an ability like Strategic Advantage because Strategic Advantage provides the cleanse first, while in this situation the cleanse would technically come after the assist.

If you have played a game like Magic: The Gathering, its best to think of effects like that: Basically the entire effects of one ability will resolve, then any other effects that triggered because of it occur (All occurring before damage, I think). Because in the Strategic Advantage case, the Cleanse is in the same effect as the assist, Daze is not a factor in choosing a target. However because "This Party's Over" does not in itself cleanse, it can only look for allies that can currently be called to assist, even if that ally would cleanse themselves by the time the actual assist comes through like JMK, because it is not the act ability with the assist that cleanses, but the act of being targeted.