Mukherjee is the "most capable and efficient leader" and has discharged his duties over the years in service of the the nation, Rangasamy told a press conference here.
Describing Mukherjee as the right choice, he said the AINRC government in Puducherry and the AINRC party as a whole supported his candidature.
He said he always had high respect for AICC leader Sonia Gandhi.
Rangasamy said Mukherjee had already contacted him over phone a few days ago and he had responded positively to his request for support.
The AINRC has a strength of 15 members in the 30-member territorial Assembly and enjoys the outside support of lone Independent member V M C Sivakumar.