kali-kālera dharma—kṛṣṇa-nāma-saṅkīrtana kṛṣṇa-śakti vinā nahe tāra pravartana

Unless one is empowered by the Supreme Personality of Godhead, Sri Caitanya Mahaprabhu, one cannot spread the holy names of the Hare Krsna maha-mantra throughout the world. Persons who do so are empowered. Therefore they are sometimes called avesa-avataras or incarnations, for they are endowed with the power of Sri Caitanya Mahaprabhu.