Hariri needs Nasrallah for his survival

Haaretz/ here

".... highly unlikely that Hezbollah operatives would have been involved in such an incident without the senior leadership's knowledge.

But Hariri's political survival depends on Hezbollah's acquiescence, something evidently more important to him than his family honor. He may also have concluded that if he supports the international probe, he will share his father's fate - or, alternatively, that doing so could risk renewed civil war between Hezbollah and his own March 14 movement. In such a face-off, Hezbollah would certainly win. Thus Hariri hopes to resolve the problem by distinguishing between the operatives and the organization........ Nasrallah denied yesterday than any of his people were involved, and lashed out at Hariri's party for "not considering the possibility that Israel was behind" the murder....."