The Brahma-gayatri, om bhur bhuvah svah tat savitur varenyam… is certainly a most powerful and purifying mantra available to the fortunate few. However, the pancharatrika diksha mantras and the Hare Krishna maha-mantra are supremely powerful, and they are available to everyone irrespective of one’s caste, creed, country, color or gender. Now let’s examine the power of the famous Gopala or Krishna mantra and the universally all inclusive Hare Krishna maha-mantra.
Sri Chaitanya Mahaprabhu said (Cc.Adi 7.73): "Simply by chanting the Gopala or Krishna mantra one will be delivered from material existence. But by chanting the Hare Krishna mantra one will get the lotus feet of the Lord," Krishna mantra haite habe samsara mocana, Krishna nama haite pabe Krishnera carana.
The Hare Krishna maha-mantra is perfect, independent, and completely pure. It requires no samskaras or initiation process to be effective. Anyone can chant this mantra whether he is qualified or not. There is unlimited power in the Hare Krishna maha-mantra. Even without a guru, initiation, sadhu sanga or anything else one could still attain Krishna-prema by chanting Hare Krishna.
By staunch faith in God, sadhu-sanga, and purity of heart acquired in a previous life, a person can attain Krishna-prema just by sitting down and chanting Hare Krishna. However, such an individual may be one out of a million. Generally, due to ignorance, aparadhas, anarthas, mental impurity, and severe lack of faith one needs training, encouragement, and association with .an advanced devotee to attain perfection in chanting the Hare Krishna mantra.
The initiation process involved in taking the Hare Krishna maha-mantra means that one accepts the shelter of a bona fide spiritual master. Receiving the guru's mercy, the disciple is guided safely and quickly on the path of spiritual perfection. Gaurkisora dasa Babaji said one can realize his svarupa just by chanting the Hare Krishna maha-mantra.
Srila Prabhupada encourages us all by saying, "The conditioned souls are engaged in a struggle for existence. Simply by chanting the Gayatri mantra, one can be delivered. Usually only brahmanas and demigods are allowed to chant this mantra. In Kali-yuga, everyone is in a very difficult position. Only a powerful mantra can deliver one from the dangers of this age. Therefore the Supreme Personality of Godhead, in His incarnation as Lord Caitanya, gives us the Hare Krishna mantra." (SB 8.6.15 p.)
"The whole thing is that Sridhara Svami is giving stress very strongly that you can simply chant Hare Krishna mantra without undergoing any ritualistic ceremonies. Madhavendra Puri has composed a nice verse wherein he says, 'My dear Gayatri mantra, I offer you my respects, but no more I can chant the Gayatri mantra.' Taking bath early in the morning is a good recommendation for spiritual advancement. But Madhavendra Puri also said, 'Now I am unable to execute this order. Please excuse me.' In this way he has described in many ways. At last he concludes that, 'I shall sit down somewhere underneath a tree, and simply remember Govinda's name. That is sufficient. Yes.' He says, 'Please excuse me, please excuse me. Please excuse me.'" (SPT 18/2/71)
Excerpt from Gayatri Mahima Madhuri by Mahanidhi Swami