TNA know that if SF wins, next will be a UNP government which rule under Ranil,Mangala,Mano,Hakeem not SF (even SF says he need some power either UNP or JVP doesn't clearly comment on that). What UNP and JVP saying is executive presidency would be abolished and all powers would be handed over to the Parliament. So SF likes it or not he should have to climb down to parliament decisions, even SF not steps down from executive president, parliament can eliminate executive powers of president. Since SF not belongs to any party he will not get any support from parliament. That’s why TNA support SF. poor SF supporters will get nothing but repentance of helping to appoint such a government