The Shiv Sena, NCP and Congress on Tuesday named Thackeray as their chief ministerial face.
The three parties have claimed support of 166 MLAs in the 288-member Maharashtra Assembly.
Devendra Fadnavis resigned as CM on Tuesday, barely 80 hours after taking oath for the second time, the move necessitated by his deputy Ajit Pawar's resignation citing "personal reasons".
Fadnavis was sworn in on November 23 in an early morning hush hush ceremony, with the support of Ajit Pawar, who then headed the 54-member NCP legislature party.
The NCP removed Ajit Pawar as its legislature party leader the same day after he took oath as the deputy chief minister of the state.
The stage is now set for Uddhav Thackeray to be sworn in as the new chief minister on Thursday.
His father late Bal Thackeray wielded the 'remote control' over the first Sena-BJP combine government during 1995-99 but never assumed a position in the government.