Prime Minister Narendra Modi entered India’s general election projecting supreme confidence. “Ab ki baar, 400 paar” went his party’s slogan, meaning this time his side was gunning to surpass 400 seats in the lower house of Parliament, a staggering majority.

But as the seven-week voting period enters its final stretch, with results expected on June 4, India is witnessing something unusual from its powerful leader. It is seeing him sweat.

As Mr. Modi crisscrosses the country for rallies in 100-degree heat, he has often appeared on the defensive, and sometimes rattled. He has frequently set aside his party’s main campaign message — that India is rising under his leadership — to counter his opponents’ portrayal of him as favoring business and caste elites. He has resorted to stoking anti-Muslim sentiments to fend off attempts to split his Hindu support base, only to deny his own words later.

Mr. Modi’s Bharatiya Janata Party, or B.J.P., is still a heavy favorite. But it is finding that the political opposition, counted out after big losses to Mr. Modi in the previous two national elections, has some fight left in it.

The opposition has found traction in challenging Mr. Modi’s control over the national narrative. With the broadcast media cowed by him, opposition leaders have turned to online platforms to find an audience for a pitch focused on economic and social justice, painting the prime minister as a primary culprit in India’s growing inequality.

Before the election, often-bickering opposition parties united in a grand alliance to confront a shared threat: what they call Mr. Modi’s mission to cripple them and remake the country into one-party rule. The alliance lost precious time in the months before the vote, bogged down by internal differences. But it has largely held together despite Mr. Modi’s efforts to lure away some of its members and sideline others with legal actions.

The alliance hopes that this translates into an improved electoral showing, after scattered votes for opposition parties in the 2019 election worked to Mr. Modi’s advantage. To have any hope of cutting significantly into the governing party’s existing strong majority in Parliament, the opposition will have to flip a large number of seats in the more populous north, where the B.J.P. is well entrenched, and hold its ground in the more prosperous south.

“The opposition realized it was now or never,” said Arati Jerath, a political analyst in New Delhi. “It had to fight Modi with all the weapons it could muster or face certain death.”

Analysts say elections that focus on local issues favor the opposition. This spring, Mr. Modi has again made a parliamentary election, contested across more than 540 seats, into a presidential-style national referendum on his own huge popularity and his achievements.

But it has become clear that, a decade into his rule, his ability to steer elections away from local concerns — and cover for his party’s parochial struggles and infighting — is waning. The opposition has tried to take advantage with an energized ground game.

In the lead-up to the vote, Mr. Modi intensified a political crackdown. Chief ministers of two opposition-controlled states were thrown in jail, and the bank accounts of the Indian National Congress, the main opposition party, were essentially frozen. “But people started campaigning door to door, village to village, state to state. So that has become really a groundwork for the opposition,” Mallikarjun Kharge, the president of the Congress party, said in an interview.

“Now they are frustrated,” he added, referring to the B.J.P.

The Congress party is trying to pull itself out of an immense hole. The rise of caste-based regional parties marginalized the once-dominant Congress in India’s electorally crucial north, and Mr. Modi’s ascendence set it back further. Mr. Modi, who had spent a lifetime working his way up from a humble background, easily cast the face of the Congress, Rahul Gandhi, as a detached, lightweight beneficiary of dynastic politics.

Just how far the Congress is trying to distance itself from that impression is evident in its election manifesto — both in form and substance.

The party’s 2019 manifesto had a fresh-faced Mr. Gandhi front and center, with a message of jobs and economic development. In the 2024 document, he wears a graying beard, a nod to the time he spent connecting with rural India during two cross-country journeys since 2022, one of them covering 2,000 miles by foot.

If that was not enough, next to him is the 81-year-old Mr. Kharge, elected in 2022 as the Congress president. His half a century in politics, and his background as a Dalit at the bottom of India’s rigid caste hierarchy, helps offset Mr. Modi’s personal story.

The Congress’s campaign promises — from cash transfers to poor women to a “guarantee of first jobs” for young people through one-year paid apprenticeships — shows that it has learned from its successes in India’s southern states, said Sugata Srinivasaraju, the author of a book on Mr. Gandhi’s struggles in leading his party.

“This is good,” Mr. Srinivasaraju said. “But the Congress does not have any emotional or cultural argument to counter” the B.J.P., with its Hindu-nationalist ideology.

The closest the Congress has come is its effort to fuse two issues: longstanding caste inequality and rising unemployment.

India’s Constitution sets aside about half of government jobs and seats in higher education for the middle and lower ranks in the caste system. With the economy struggling to create enough private-sector jobs, these government positions are seen as crucial for any hope of economic mobility.

The Congress’s call for a census of Indians by caste — there has been no official national data on the size of each caste for decades — appears to be striking a chord. The party says such an exercise would ensure that marginalized Indians get their rightful share of slots.

That push is also furthering two charges aimed at Mr. Modi: that he has overseen an economy that benefits only billionaires, and that his party has an upper-caste bias. While it is true that the B.J.P. was once an upper-caste, urban party, Mr. Modi has broadened its base by bringing in lower castes. But his response to the charge suggests he is nervous that the label may stick.

“He’s for the rich,” Mr. Kharge said at a large rally in Mumbai. “He has done nothing for the poor.”

Behind Mr. Kharge were the leaders of several parties in the alliance, each of whom would draw on a grievance to depict Mr. Modi as dangerous for India.

One of them, Arvind Kejriwal, made a particularly personal case that Mr. Modi is trying to turn the country into something like Russia under President Vladimir V. Putin — “one nation, one leader.”

“I am coming straight from jail,” Mr. Kejriwal began his speech.

His Aam Aadmi Party holds power in the Delhi region and in the northern state of Punjab. Its expansion is a threat to Mr. Modi, whose government arrested Mr. Kejriwal over corruption allegations just before the election, creating the absurd reality in which India’s capital was being run from a jail cell.

Mr. Kejriwal managed to get a three-week bail during the campaigning. As he jumps from rally to rally across the country, his connection with crowds makes clear why Mr. Modi would have liked to keep him behind bars.

In Mumbai, he painted India under Mr. Modi as a dystopia where anyone who gets in the prime minister’s way will be locked up. Mr. Kejriwal said he had been kept under the surveillance of multiple cameras in jail — “watching what time I wake up, what time I go to the bathroom, how long I sit on the toilet.”

Then he made his final appeal. This election, he said, is a vote for either keeping him in jail or restoring his freedom. He will be watching the results on June 4 from his cell.

“You can write me letters,” he said. “Cell No. 25, Jail No. 2, Tihar Jail.”