Sonia Gandhi leading a march of over 100 members of Parliament belonging to 14 political parties to submit a memorandum to President Pranab Mukherjee, India’s constitutional head, against a controversial new land acquisition law Prime Minister Narendra Modi’s government wants to enact, suddenly unveiled a united opposition which has the potential to change India’s political landscape.

The live telecast of the dramatic Gandhi-led opposition rally from Parliament House to Rashtrapati Bhawan, or the presidential palace, brought home to many that a broad alternative to Modi’s Bharatiya Janata Party-led National Democratic Alliance not only exists but is trying to stage a comeback by tapping the power of unity.

The allies who marched under Gandhi’s leadership on March 17 — Trinamool Congress, Dravida Munnetra Kazhagam, National Congress Party, Indian Union Muslim League, Communist Party of India, Communist Party of India (Marxist), Janata Dal (Secular), Janata Dal (United) and Samajwadi Party, revived memories of the Congress Party-led United Progressive Alliance, which was in power for two successive terms with Manmohan Singh as prime ministers before badly losing to the NDA 10 months ago.

The march, which turned into a media event, highlighted the ability of the Congress Party to mobilize the full range of non-NDA parties for a good cause despite being reduced to just 44 MPs in the Lok Sabha. It also underlined Gandhi’s acceptance as the tallest opposition leader across the board. Naturally, it augurs well for the Congress, but is bad news for the BJP.

Moreover, opposition unity can derail Modi’s economic plans and dent his image as someone who brooks no delays. The opposition, which has ganged up against the new land acquisition law Modi is bent upon enacting, is demanding the right to fair compensation for farmers and transparency in acquiring land. The new law Modi has proposed would mean projects in defense, rural electrification, rural housing and industrial corridors would not need to seek the consent of 80 percent of the affected landowners as earlier mandated — and acquisitions would be exempted from holding a social impact study involving public hearings — procedures industry objected to on the grounds that it delayed any acquisition process by years.

Fights between farmers and companies trying to find land for industrial projects has hampered India’s plans to expand its network of highways, build mines and other infrastructure, holding up about $300 billion of investment. Modi says India’s poor infrastructure is the main impediment to economic growth needed to help lift hundreds of millions of people out of poverty.

Modi has successfully raked in billions of dollars through the sale of coal blocks and telephone spectrum and raised foreign investment in the insurance sector. But the land acquisition law has became a major embarrassment with rival parties, particularly the Congress, Trinamool Congress and the Left, not only blocking it in the upper house of Parliament where NDA is in a minority but petitioning the president to intervene.

Sonia’s emergence as the supreme opposition leader is note-worthy because Modi denied her the Leader of Opposition (LoP) post in the Parliament as the Congress has only 44 MPs whereas at least 53 MPs are required to get the prized post, which is equivalent to a Cabinet minister. The Congress’s interpretation of the rule is that although it doesn’t have the requisite numbers on its own, it’s entitled to the post by virtue of being the biggest opposition party enjoying the backing of smaller opposition parties.

However Speaker Sumitra Mahajan, who belongs to the BJP, refused to buy the Congress argument. In that sense, Gandhi’s high-voltage march at the head of dozens of MPs and leaders belonging to 14 opposition parties, is sweet revenge for denial of the LoP post.

But with Sonia leading from the front, will the promotion of Rahul Gandhi to the post of Congress president in April, be put on hold? Soon after plans to anoint him leaked out last month, Rahul suddenly vanished instead of leading his party’s charge against the land law. In his absence, his mother — who has serious health issues and had virtually gone into semi-retirement — has done such a commendable job that many feel Rahul needs more training before he can fill his mother’s shoes.