Imamah (Arabic: إمامة‎) is the Shia Islam doctrine (belief) of religious, spiritual and political leadership of the Ummah. The Shia believe that the Imams are the true Caliphs or rightful successors of Muhammad, and further that Imams are possessed of divine knowledge and authority (Ismah) as well as being part of the Ahl al-Bayt, the family of Muhammad. These Imams have the role of providing commentary and interpretation of the Quran as well as guidance to their tariqa followers as is the case of the living Imams of the Nizari Ismaili tariqah. 

Shias believe that Imamah is of the Principles of Faith (Usul al-Din).As the verse 4:165 of quran expresses the necessity to the appointment of the prophets; so after the demise of the prophet who will play the role of the prophet; till the people have not any plea against Allah.So the same logic that necessitated the assignment of prophets also is applied for Imamah.That is Allah Must assign someone similar to prophet in his attributes and Ismah as his successor to guide the people without any deviation in religion. They refer to the verse (...This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as religion...) 5:3 of Quran which was revealed to the prophet when he appointed Ali as his successor at the day of Ghadir Khumm.
Does it support their views?
 logic that necessitated the assignment of prophets also is applied for Imamah