The term and concept of Dalit-Bahujan (meaning combined Dalit society irrespective of sub-caste) is a concept that was invented and acted upon successfully by the late Kanshi Ram.
One of the biggest problems that stand in the way of Dalit unity is the existence of sub-castes among them, which of course again is concurred to be a Brahminical ploy to keep them divided.
Kanshi Ram saw that if all the Dalits could be united under a common banner as all of them more or less face the same discrimination problems, it could not only translate into political power for the Dalits but would also give them a powerful voive in Indian society.
Of course, the focus was not only on uniting the Dalit castes but also the numerous Sudra castes and those clubbed as Scheduled castes and tribes.
Kanshi Ram succeeded at it resulting in the formation of the Bahujan Samaj Party (BSP) which along with the Samajwadi Party(SP), another low caste party on the lines of the BSP has wrested power from the traditional political parties and have been ruling the North Indian state of Uttar Pradesh for most of the last two decades.
The Dalit-Bahujan concept has caught on and is slowly growing in strength though not at the rate as it should be.
Many Dalit intellectuals, writers and thinkers like Kancha Illaih and Udit Raj now operate on the concept of Dalit-Bahujans rather than striving against caste drscrimination only against the Dalits.