Sonia Gandhi, who gave the opposition rally in Kolkata a miss, called it an "important attempt" to galvanise leaders across the political spectrum to fight the "arrogant and divisive" Narendra Modi government.
In her message to the rally, the Congress stalwart wished the event "all success".
"This rally marks an important attempt to galvanise leaders across the political spectrum to fight the arrogant and divisive Modi-rule. I wish them all the success," she said.
Leader of Congress in the Lok Sabha Mallikarjun Kharge, who represented the party, along with its spokesman Abhishek Manu Singhvi read out the message at the Brigade Parade ground organised by Trinamool Congress chief and West Bengal Chief Minister Mamata Banerjee.
Senior leaders of 23 political parties attended the rally.
Painting a grim picture of the country, Gandhi said: "Crisis looms across our farmers and extends to our borders; the youth are jobless; rice and jute farmers are under stress and fishermen are incurring deep losses.
"The country at large is under immense strain -- economically our citizens have been screeched, politically our institutions have been undermined and socially our pluralistic fabric stands vitiated."
The former Congress president said the upcoming Lok Sabha election would not be an "ordinary one".
"This will be an election to restore the nation's faith in democracy, defend our secular ethos and heritage; and defeat the forces that are trying to sabotage the Constitution of India."
(With IANS inputs)