Sankaradeva's Religion - Mahāpurusism
The name of the religion preached by Sankaradeva is Eka-Sarana Hari-Nām Dharma, also referred to as Mahāpurusism or simply, Assam Vaisnavism. It is deeply rooted in the Vedantic philosophy, as contained in the Bhāgavata, the Gitā and other sacred texts.
Mahāpurusa - The Supreme Being
Mahāpurusa (The Supreme Being) is an epithet of Visnu in the Bhāgavata Purāna (11.5.33-4) and Pariksita is called a Mahapaurusika (2.1.10) for his becoming a devotee of that Mahāpurusa. The epithet is found to have been used in this context by Madhavadeva, the Saint's foremost disciple and successor, in his celebrated work the Nām Ghosā in verses 393 and 646-47. Thus, the expression Mahāpurusiya Dharma or Mahāpurusism implies faith or devotion to the Mahāpurusa (Nārāyana-Visnu-Krishna).
The term Mahāpurusa, in Sankaradeva's religious system, is applied to God and hence, the term Mahāpurusism, like Zoroastrianism, Buddhism, Christianity or Muhammadanism, is not commemorative of its propounder, as many people wrongly hold. It is only in comparatively recent times that this epithet came to be secondarily applied to Sankaradeva and his successor, Madhavadeva.
The religion preached by Sankaradeva stresses on unqualified devotion to God in all the aspects of the term Mahāpurusa, and it is the reason why it is rightly called Mahāpurusiyā Dharama (Mahāpurusism). We find in the holy Nām Ghosā the very exact epithet Mahāpurusa very significantly used of God:
Suka nigadati Pariksita / yadi āmi nirgunata sthita,
Tathāpi uttama slokara mahimā gune:
Karileka vasya mora citta / Bhāgawata grantha biparita,
Parama ānande padhilo mai āpune. 
Tomāka kahibo sehi sāstra / tumi tāka sunibāra pātra,
Mahāpurusara sewaka tumi samprati:
Suka says, O Pariksita, although I stand for nirguna I have been so impressed by the glory of the excellent verses that I have myself gone through the wonderful scripture named Bhāgavata with great joy. I am going to read that scripture to you, for you are worthy of hearing it being now a servant of the Mahapurusa.
The Mahapurusa of the Bhāgavata is referred to as Purusottama in the Bhagavad Gitā and also as Parama Purusa. As Madhavadeva says in his Nām Ghosā:
Ksara pade ito / dehak bolay / aksar sabade Brahma:
Duito kari Hari / uttama nimitte / prakhyāt Purusottama.
Ksara refers to this body; aksara to Brahma (Ego); Hari (God) being superior to both is well known as Purusa Uttama (Supreme Soul).
Purusa Uttama / Parama Purusa / Parama ānanda Swāmi:
Tayu pāda-padma / makaranda āse / sarana pasilo āmi.
Thou the best Purusa, the Supreme Purusa and Master of Supreme Joy. I seek refuge in thee for the nectarine juice of thy lotus feet.
Sankaradeva accepts this Mahapurusa, Purusottama and Parama Purusa to be identical with Vāsudeva Sri Krishna, the son of Nanda and Yasoda, who is all-perfect and is Bhāgavat (Supreme Divinity) Himself. Thus, in his religion, one seeks to realize the nirguna (attributeless) Mahapurusa through the gunas (attributes) of Lord Krishna.
Therefore, constant recitation of the nāma (Name) of the Lord (Krishna or Hari), which are descriptive of His gunas, is stressed upon. This must, again according to Sankaradeva, be done with single-minded devotion and by taking refuge in Him alone (Eka-Sarana). It is for this reason that Mahāpurusism is popularly referred to as Eka-Sarana Hari Nām Dharma.