He, at the same time, also said that Rahul Gandhi was "uniquely poised" to lead such an effort.
Speaking at the launch of his book, "Tidings of Troubled Times", Tewari said the Congress cannot fight alone without the support of right-thinking people.
"The grand alliance is needed not for electoral reasons but to save the founding vision of India," he said.
"We have to win 2019 (Lok Sabha elections) to change the situation. Where we are strong, we have to fight to the last and where we are not strong, put right alliances in place," he said.
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In the current atmosphere, there is no room for dialogue and no moderation in the discourse, he added.
"The pushback to (Donald) Trump in the US is intense and well-thought of. This is not happening in India. Corporate ownership of media is not a new phenomenon. They have stood up to Emergency. It is not happening now. This is worse than undeclared emergency," the Congress leader said.
"But Vajpayee was leading a coalition government. Now this is a majority government, and it is reflected from the way they treat their allies. This is a majority government with majoritarian ethos, which believes some Constitutional provisions are not to their liking and need to go," he said.
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