The question is thus - is ultimate authority over affairs of the state lies with God or with Ummah (The people). And if we believe it is with God, will that state need a religious ruler. And if God is to give guidance through a spiritual ruler, who will make sure the ruler is just and not a tyrant.
Now, Twelver Shi'ism differs from the Sunni tradition in a handful of important ways — not only in its belief in who was the legitimate heir to the Prophet Muhammad's leadership of the community of the faithful after his death, but also in its attitudes toward political authority and devotion. But one of the most important differences is the Shi'ite tradition's unique practice of ijtihad — the use of independent reasoning to pass new religious rulings. This is absent in Sunni tradition which limits possibility of political adaptability of Islamism to politics.
That much is clear is the very history of the Islamic Republic. In the early 1970s, Ayatullah Ruhollah Khomeini deviced a new model for Shia government. Khomeini was a marja al-taqlid (a model of emulation), and he interpreted the Koran and Hadith to conclude that God had decreed for Islamic government — in the absence of the Twelfth Imam, who would return one day in the messianic tradition and launch his own reign of justice. Khomeini called this vision of the clergy being given authority over governance "velayat-e faqih", or guardianship of the jurist. This religious ruling is frowned upon by "traditional" ayatollahs, who advocated withdrawal of clergy from politics - so called quetism; to this school Grand
One of the many devotional pictures showing unusually the face of the Prophet and Family. This picture represents the prophet Muhammad in the middle, with his veiled daughter Fatima on his left hand side, his cousin and son in law on his right hand side, and his two grandsons, Ali's og Fatima's sons, Hasan (in green) and Husayn (in red). "The holy family" or "the Holy Five" has a high position among all Muslims, but particularly among Shia Muslims. Behind Muhammad stands an angel (Gabriel) with the Quran in his hands. for the angel Djibril was the one who brought the first revelation to Muhammad on that very night, the night of Power. In this picture, like in many other representations of Ali, he holds in his hands one of his characteristics, the double pointed sword Dhu 'l-Faqar.