Mr Kumar's break-up with the BJP has been described as a bloodless coup.
The Mahagathbandhan 2.0 will begin where the first alliance between Nitish Kumar and the Rashtriya Janata Dal had left off, sources in Lalu Yadav's party have indicated. Tejashwi Yadav will be back as Mr Kumar's deputy and his elder brother Tej Pratap Yadav will be in the cabinet, sources said.
While Mr Kumar's break-up with the BJP has been described as a bloodless coup, the path of the split and the details of the next government were being worked out over the last three or four months, sources indicated.
The job was made complicated by Mr Kumar's harsh comments on Tejashwi Yadav -- accused in an alleged corruption case -- when he ended the Grand Alliance with the Congress and the RJD.
"I felt suffocated, my conscience pricked me... there was no other way," he had said after resigning in July 2017. In an apparent reference to the Yadavs, he had said, "It wouldn't be right if I didn't take a stand, I don't do politics of this kind".
But over the last months, both sides have worked hard to overcome their differences and are more comfortable with each other's working style.
The journey had apparently started back in May, when Nitish Kumar walked the short distance to Tejashwi Yadav's home for an Iftaar party he was holding. It was followed by a return visit from Tejashwi Yadav at Nitish Kumar's Iftaar party.
As the young leader left, the Chief Minister had walked him back to his gate in full view of the media -- a loaded gesture which was not missed by anyone.
The journey, sources indicated, was made under the careful eye of Lalu Yadav, Mr Kumar's friend-turned-foe and back again.
Mr Kumar announced his split with the BJP at a meeting of his party legislators this afternoon. He is expected to meet the Governor later today – a meeting where he will be accompanied by Tejashwi Yadav and other leaders supporting him, sources said.