He got the final go-ahead from party chief Sonia Gandhi on Thursday morning. Gandhi reportedly said he is the best candidate to win the poll.
While many in the UPA were shocked at Mulayam Singh Yadav's sudden U-turn, Mukherjee maintained he never lost confidence in Yadav.
His OSD Pradip Gupta touched his feet at the parking bay of 7 RCR itself. His long-time confidante Omita Paul and Pradyut Guha were the first to greet him while the peons distributed sweets. Mukherjee's daughter Sharmishta soon joined the celebrations.
In the UPA's meeting, J&K chief minister Omar Abdullah said the UPA should announce its candidate otherwise an impression is going that: "An ally is controlling the government." On this, NCP chief Sharad Pawar said the announcement should be made only if the UPA has support from SP and BSP.
Gandhi, PM and Mukherjee said both the BSP and SP have assured them of their support.
PM asked Pawar if PA Sangma had his blessings. But Pawar said no. In fact, Praful Patel at this point said Sangma had lost the poll even before the contest.
PM and Gandhi also asked Pawar to talk to other parties.
Mukherjee pointed out that if Kalam is in the race it would be a keen contest.
To this, Patel said: "Kalam will not enter the contest once he comes to know that Mulayam Singh Yadav is supporting you. He will back out."