Here are the top 10 points in this big story:
Charanjit Channi, 58, - a three-time MLA from Rupnagar's Chamkaur Sahib - will be sworn in as Punjab's first Dalit Chief Minister 11 am. The Congress hopes his deputies will be from the Jat Sikh and Hindu communities, the party's state-in-charge, Harish Rawat, said.
Sources said Dera Baba Nanak MLA Sukhjinder Singh Randhawa - earlier linked strongly to the top post - had been picked as the Jat Sikh Deputy Chief Minister. The deputy from the Hindu community could be one of Brahm Singh Mohindra (the Patiala (Rural) MLA), Vijay Inder Singla (the Sangrur MLA) or Bharat Bhushan Ashu (the outgoing Food and Consumer Affairs Minister), according to news agency ANI.
Mr Channi's elevation is key given next year's election and the fact Dalits are around 31 per cent of Punjab's population. The math is simple - the Akali Dal (earlier in power with the BJP) has joined with Mayawati's Bahujan Samaj Party to tap Dalit votes. Mr Channi - as a Dalit Sikh face - the Congress hopes, will counter that vote flow.
The Congress' choice has triggered criticism, given he was accused of sexual harassment by a woman IAS officer. Mr Channi allegedly sent an inappropriate text in 2018, but the officer never filed a complaint. The claim resurfaced in May after the state's Women's Commission sent a notice asking for the state government's response.
Amarinder Singh has offered his "best wishes" to the new Chief Minister and a subtle reminder of the magnitude of his new task. "My best wishes to Charanjit Singh Channi. I hope he's able to keep the border state of Punjab safe and protect our people from the growing security threat from across the border," he said.
Rahul Gandhi also offered his congratulations, and reminded Mr Channi of the task at hand - to fulfill promises made to the people of Punjab. Mr Gandhi is expected to be present at the oath-taking ceremony, which will be restricted to around 40 guests, according to ANI, in view of the Covid pandemic.
Sunday morning's meeting of the legislature party was postponed after Rajya Sabha MP Ambika Soni - believed to be the party's first choice for Chief Minister - declined the offer. Ms Soni said "no" at a late-night meeting with Rahul Gandhi; she stressed on the "ramifications" of a non-Sikh Chief Minister, particularly with an election due.
Yesterday Amarinder Singh said he had been "humiliated" and quit. His resignation followed months of sniping with rival Navjot Sidhu; the final nail in the coffin was Saturday evening's meeting of Congress MLAs. Sources told NDTV around 50 of the party's 80 MLAs wrote to Sonia Gandhi and asked for Mr Singh to be replaced.
A furious Mr Singh told Mrs Gandhi he had had enough. "I was humiliated three times by Congress leadership..." he said. He wrote declaring himself "anguished" and defended his administration's track record. The Captain also told NDTV that though he had resigned, "... for the sake of my country, I'll oppose his (Navjot Sidhu) name..."
The Singh-Sidhu feud dates to the 2017 election; Mr Sidhu hoped to be Deputy Chief Minister but was reportedly denied by Mr Singh. The rift escalated sharply in recent weeks and a tenuous truce unravelled after statements by Mr Sidhu's advisers. Last month, fresh complaints against Mr Singh set the stage for the weekend's drama.
With input from ANI