"I congratulate you for becoming the next President," Tuki said in a statement.
Tuki, with almost all legislators of the state Legislative Assembly, had met Mukherjee at Guwahati on July 6 last, and had assured absolute majority from the state.
In the election, held on July 19, Mukherjee got 54 votes from the 60-member legislative assembly.
While one Congress MLA Jomin Tayeng could not vote due to ill health, two went in favour of P A Sangma, Mukherjee