"It is obvious the enemy of our people is determined to undermine the 20 years of achievements of our democracy," MKMVA said in a statement.
The "Sidikiwe! Vukani! Vote no!" campaign calls on South Africans to either vote for a minority party, or spoil their ballots.
It was launched at the University of the Witwatersrand on Tuesday by Kasrils and former deputy minister Nozizwe Madlala-Routledge.
"If the ANC were to lose three, four percent in this election they'll still be in power, nothing will stop that," Kasrils told reporters at the launch.
The MKMVA said it would mobilise South Africans to vote for the ruling party.
"We will occupy our defence posts and mobilise the people of South Africa to vote for the ANC.
"The only way to guarantee a better future for the overwhelming majority of our people is to vote for the ANC."
It said there was no other government in South Africa's history that had "delivered so much to its own people in a period of 20 years like the ANC-led government".
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