Patna (NDTV): Nitish Kumar has quit as Chief Minister of Bihar, ending the two-year-long political experiment that was branded as a game-changing Maha-gathbandhan or Grand Alliance which included his party, Lalu Yadav and the Congress. This evening, Mr Kumar met with Bihar Governor Keshari Nath Tripathi to deliver his resignation. He has transitioned already into an arrangement with the BJP.

His stunning move came after Lalu Yadav reiterated earlier today that his son, Tejashwi, would not quit as No 2 in the government despite being caught in a corruption scandal. "I did not ask for anyone's resignation," said Nitish Kumar, "but I told Tejashwi and Lalu that they must explain the charges publicly. The atmosphere had become such that it was impossible to work," he said, adding "my conscience told me to quit."

A Plan B was well-developed. BJP leaders met in Delhi and Patna and agreed that the party will support Nitish Kumar, ensuring he wins a trust vote, and they will together run a new government. On Twitter, Prime Minister Narendra Modi congratulated Nitish Kumar for "joining the fight against corruption" and the Chief Minister thanked him, also on Twitter.

Through the day, events pointed to a climax of the political drama that has raged in Bihar for weeks. The Governor reportedly changed his travel plans to stay back for the meeting requested by the Chief Minister. Lalu Yadav, due to fly to Ranchi for a court appearance tomorrow, decided to drive there instead of flying, which allowed him to remain in Patna for a few extra hours at a crucial time.

On July 7, Lalu and Tejashwi Yadav were named in a corruption case by the CBI which searched their Patna home. The Yadavs have attributed the case to a get-even attempt by Prime Minister Narendra Modi who they allege is "scared" of their concerted opposition to him. Nitish Kumar said the defense didn't wash, stressed that his "zero-tolerance to corruption" policy is unwavering, and amply hinted that Tejashwi Yadav should rise to the occasion by opting out of the government.

Today, Lalu Yadav's party met and repeated that not only will Tejashwi Yadav remain in office, but that the Chief Minister's suggestion of a public and detailed defense has not been accepted.

Statements from both sides today indicated the confrontation was past the point of rescue.

"I have known Nitish for 40 years, he is no saint," said Shivanand Tiwari, a senior member of Lalu Yadav's party. "We can't compromise on Nitish's clean image," said KC Tyagi, a senior leader from the Chief Minister's party.

The Congress' top bosses, Sonia and Rahul Gandhi, have attempted mediation with both Nitish Kumar and Lalu Yadav, but were unable to broker a compromise.

The sudden death of the Bihar alliance will considerably wind the attempt of the opposition to build an 18-party front that hopes to prevent Prime Minister Narendra Modi from winning a second term in 2019. The league was fashioned on the Bihar alliance which saw former rivals Nitish Kumar and Lalu Yadav quitting their differences in 2015 and co-signing with the Congress to ensure that their collective support groups - a range of castes - became the wall that PM Modi ran into as he led the BJP's campaign in Bihar.