For years, Prime Minister Narendra Modi of India has moved his country closer to the United States, in particular by focusing on his relationship with President Trump, whom he has called a “true friend.”

The much-touted bond, nurtured through platitudes and joint appearances at stadium rallies during Mr. Trump’s first term, led one television anchor sympathetic to India’s leader to coo that “they have extraordinary chemistry.” Another chipped in: “When the two of them are onstage together, it is like lightning.”

But just when Mr. Modi needed to lean into that relationship, he has instead had to weather a series of blows from Mr. Trump that is hurting his strongman reputation at home. Indian officials are wondering how the historic highs in the relationship have soured so quickly.

Mr. Trump’s announcement on Wednesday that he was slapping 25 percent tariffs on India, as well as an unspecified additional penalty for India’s economic ties to Russia, was just the latest in a series of slights. Mr. Modi has also faced a storm of criticism over the Trump administration’s treatment of India, which it has seemingly been treating as an equal to its smaller archnemesis, Pakistan.

Analysts and officials in New Delhi say the damage runs deeper: It has thrown off a relationship that has been built painstakingly for decades, one that recognized India’s balancing act in a difficult region where China and Russia loom large. India had been allowed to quietly grow closer to the United States on its own terms and has taken a firmer stance on China.

“One of the attributes of Indian foreign policy in the past 20 or 25 years is that we built an equation, at the leader level and at the systemic level, with America through thick and thin, through multiple transitions,” said Ashok Malik, the chair of the India practice at The Asia Group and a former adviser to the Modi government. “That has been shaken.”