Many people are surprised to learn that Kṛṣṇa is Svayaṁ Bhagavān, the original form of Bhagavān and the source of all avatāras including Rāma and Visṇu himself. Śrī Jīva Goswami in the Kṛṣṇa Sandarbha does an exhaustive analysis to establish Kṛṣṇa as Svayaṁ Bhagavān. Śrī Babaji has recently translated this book (available at the above link) with insightful commentary. The commentary to Anuccheda 80 is reproduced below.
In Anuccheda 28, Śrī Jīva Goswami cited the verse: kṛṣṇas tu bhagavān svayam (SB 1.3.28), and offered a detailed explanation to establish that Kṛṣṇa is the original form of Bhagavān. He specified this verse as a a परिभाषा-सूत्र, a universal or governing rule, comparing it to a victorious emperor that prevails over all other statements. Then in the following anuccheda (29), he drew attention to various verses that seem to contradict this conclusion, reinterpreting them in the light of the above verse.
In Anucchedas 30-43, Śrī Jīva cited numerous verses that are supportive of the emperor verse. Then in Anucchedas 44-73, he examined the heart of the principal speakers and students within the Bhāgavata purāṇa itself, showing that the intent of all of them was to speak and hear exclusively about Śrī Kṛṣṇa. In Anuccheda 74, he further analyzed the Bhāgavata purāṇa with reference to the six pramāṇas of Pūrva-mīmāṁsā, viz. श्रुति, लिंग, वाक्य, प्रकरण, स्थान and समाख्या, confirming once again that the Bhāgavata purāṇa’s primary subject is Kṛṣṇa. Then, beginning from the last part of Anuccheda 74 upto Anuccheda 79, he discussed other verses that are representative of the emperor verse, in the sense that they directly confirm its meaning.
This entire analysis was based directly on the Bhāgavata purāṇa. Now in this anuccheda, Śrī Jīva argues that even other śāstras accept Kṛṣṇa as Svayam Bhagavān. This is called gati-sāmānya-nyāya, or the principle that all scriptures share a common purpose. Because all the scriptures, such as the Vedas, Purāṇas, Upaniṣads, the Mahabhārata, the Gītā, and the Vedānta-sūtra, have a common author whose sole aim is to benefit humanity in the ultimate sense, they must have one prime subject. Sri Jiva illustrates this by referring to the Mahabhārata, the Gītā, Brahma-samhitā and Padma Purāṇa. In this context, the following statements may be considered:
O Devī! All avatāras emanate from the Supreme Brahman in the form of Kṛṣṇa. But Kṛṣṇa, who is both inclusive of attributes (saguṇa) and beyond all attribution (nirguṇa), is the avatārī Himself. (Nārada Purāṇa 2.58.45)
I have described to you the unlimited avatāras. I shall now explain categorically that Kṛṣṇa, however, being Svayam Bhagavān, is supreme among them. (Śrī Kṛṣṇa-saṁhitā, Chapter 92)
All these avatāras are either portions or minute portions of the Puruṣa, but Kṛṣṇa is Svayam Bhagavān. (Brahmā-vaivarta Purāṇa 4.117.12)
Śrī Jīva now raises an objection to his own thesis. This is called स्थुण-निखनन-न्याय, or the principle of driving in a post to make it settle firmly in the ground. In the Uttara-khaṇḍa of Padma Purāṇa (Chapter 80), Nārāyaṇa is described as the support and source of everything. Similarly in the Pañcarātra literature, Vāsudeva is said to be the source. For example, the Sātvata-saṁhitā and Lakṣmī-tantra prescribe the worship only of the catur-vyūha, and Vāsudeva is specified as the source of the other three members. Ahirbudhnya-saṁhitā also declares that everything upto and including Saṅkarṣaṇa dissolves into Vāsudeva:
He [Saṅkarṣaṇa] entered into that eternal Bhagavān Vāsudeva. O Sage, at that time there was neither asat (non-being) nor sat (being). (Ahirbudhnya-saṁhitā 4.68)
The latter text goes on to describe that Vāsudeva alone remains upon the dissolution. All this apparently contradicts the conclusion that Kṛṣṇa is Svayaṁ Bhagavān. It cannot be argued that in these descriptions Nārāyaṇa and Vāsudeva are mere references to Kṛṣṇa because They differ not only in name, but also in form, associates, and abodes. How, then, can one conclude that Kṛṣṇa is Svayaṁ Bhagavān instead of Nārāyaṇa or Vāsudeva?
In response to this doubt, Śrī Jīva reminds us that the Śrīmad-Bhāgavata has already been established as the highest authority in the self-disclosure of the Absolute as Bhagavān. If a contradiction appears to exist between the Bhāgavata and any other scripture, the former takes precedence over the latter. This is called balābala-vicāra, or the estimation of relative judicial strength. The Bhāgavata Purāṇa is the last work of Vyāsa and is, therefore, understood to be the most authoritative of his compositions. As we have learned already, the general rule of hermeneutics is that a later injunction is stronger than earlier ones (पौर्वापर्ये पर-विधिर् बलवान्, Anuccheda 28.2). This principle is also applicable to books written by the same author.