“He could hope he could change some minds,” Mr. Rangaswami said. “It could happen.”

Mr. Trump crowed last week that his decision to join Mr. Modi at the event on Sunday enlarged the crowd at the stadium, which can hold up to about 70,000 people.

“I have a very good relationship with Prime Minister Modi. By the way, great relationship with Pakistan and with India,” Mr. Trump told reporters on Air Force One several days ahead of the Modi event. “But he’s got a big crowd coming, and I guess the crowd just got a lot bigger because they just announced — he asked would I go, and I will go.”

Mr. Trump’s appearance at the event, which was followed by a stop with the Australian prime minister at an Ohio recycled packaging plant owned by an Australian company, comes as his administration is finalizing plans for a modest trade deal with India. That step that would help resolve earlier tensions between Mr. Trump and Mr. Modi over India’s trade balance with the United States and other trade issues.

The trade agreement, which could be finalized by the two leaders as soon as this week, is expected to help American farmers and manufacturers by eliminating Indian restrictions on electronics, medical devices and a few agricultural goods. In return, Mr. Trump would restore a special trade status for developing countries, something the president stripped from India this year.

Resolving a nettlesome trade dispute with India presents Mr. Trump with an opportunity for a public relations victory amid increasing frustration over his global trade wars with China and other countries.

Mr. Modi, 69, is at his best outside India. He has prioritized, more than any other Indian leader in recent decades, India’s brand around the world and projected an image of a muscular India, an emerging superpower. He travels all across Asia, he was the first Indian prime minister to visit Israel, he has journeyed across Africa and during a visit to New York in 2014 he packed Madison Square Garden with ecstatic crowds cheering: “Modi! Modi! Modi!”

He has come a long way. Years ago, he was banned by American authorities from even entering the United States because of allegations that as chief minister in Gujarat in the early 2000s he was responsible for an explosion of religiously driven violence that claimed more than 1,000 lives, most of them Muslim.