Muhammad b. 'Ali, were extremely important, not so much by reason of their numbers as by their excellent organisation. They had developed a regular system of missionaries (da'i, plur. du'at) who travelled under the guise of merchants and confined their teaching to private instructions and informal intercourse, a method which has become the standard type of Muslim missionary propaganda. By Abu Hashim's death and legacy Muhammad b. 'Ali found this very fully organised missionary work at his service, and its emissaries were fully confident that his acceptance of the overtures of the Shi'ite deputation meant that he stood as the champion of Shi'ite claims. The stricter Shi'ites who followed the house of al-Husayn did not admit the claims of Muhammad b. al-Hanafiya or his descendants, but they supported Muhammad b. 'Ali's efforts under the impression that he was a Shi'ite champion.
The propaganda in favour of Muhammad b. 'Ali is sometimes referred to as 'Abbasid because he was descended from al-'Abbas, one of the three sons of 'Abdu l-Muttalib, and so brother of Abu Talib the father of the Imam 'Ali and of 'Abdullah who was grandfather of the Prophet Muhammad. At the time, however, the missionaries claimed rather to be the supporters of the Hashimites, a term which was ambiguous, perhaps intentionally so. It was afterwards explained as referring to the house of Hashim which was the rival clan of the Quraysh opposed to the 'Umayyads and that to which the Prophet, and 'Ali,
