Amit Shah was convinced by the BJP's leadership in Karnataka (File)

Showing remarkable momentum on Karnataka three days after the HD Kumaraswamy-led coalition government fell in a trust vote, the ruling BJP gave BS Yediyurappa the go-ahead in the early hours of this morning to stake claim to power. The clincher, say sources, was a video call between Karnataka BJP leaders and rebel lawmakers whose resignations enabled the coalition's collapse.

Mr Yediyurappa took reporters by surprise when he headed to Governor Vajubhai Vala's house this morning, declaring that he was staking claim and wanted his oath ceremony by evening. It seemed to be a sudden move at a time the BJP seemed to be in no hurry to shake things up in Karnataka.

Sources say the BJP's central leadership, chary of forming a minority government that could fall, came on board after Karnataka leaders assured that rebel Congress and Janata Dal Secular lawmakers would back them on the floor of the assembly.

Mr Yediyurappa is inclined to take the trust vote on Monday, two days before his July 31 deadline to prove his majority.

What convinced his bosses Amit Shah and JP Nadda to accept his plan to form government was an early morning video call between rebels stationed in Mumbai and top Karnataka leaders. "The assurance was communicated to the central leadership this morning. The nod came from Amit Shah early this morning. Only then did Yediyurappa meet the governor," a BJP leader told NDTV, dismissing speculation that the leadership was unconvinced.

At 76, Mr Yediyurappa has been able to dodge his party's 75-plus age ban. The three-time Chief Minister has never completed a term and hopes the fourth time's a charm. Apparently for better luck, he even changed the spelling of his name from "Yeddyurappa" to "Yediyurappa" - as confirmed by his Twitter bio.

In May last year, his stint lasted 48 hours after the oath ceremony; as the Congress and Janata Dal Secular teamed up to stop the BJP from taking power, Mr Yediyurappa was forced to quit moments before a trust vote.

For a year, the coalition accused Mr Yediyurappa of working to "Operation Lotus", the name given by critics to what they call the BJP's strategy of seizing power by drawing away lawmakers with money or other inducements.

A flurry of resignations in the coalition this month finally paved the way for a change of regime.

Former state minister and BJP parliamentarian Shobha Karandlaje, considered a Yediyurappa loyalist, rejected suggestions that the BJP central leadership wanted to adopt a more cautious approach and wait for a few more days.

"Yediyurappa staked claim to form the government only after getting a nod from the central leadership. He and the central leaders are on the same page," the Lok Sabha member said.