Top Congress leader Narhari Amin has joined the Bharatiya Janata Party (BJP).
Gujarat chief minister Narendra Modi welcomed the former deputy chief minister to the party on Thursday morning.
"Shri Narhari Amin´s joining BJP strengthens democracy and destroys dynastic politics - a momentous event in Guj(arat) politics," said Modi on micro-blogging site Twitter.
A number of Amin supporters also quit the Congress.
Amin, who had been with the Congress for 25 years, left the party last week after he was not given a ticket to contest in the Assembly polls in December.
Gujarat will vote in two phases on December 13 and 17.
The results will be declared on December 20.