Ann Arbor, Michigan - On his first year anniversary as India's prime minister, Narendra Modi refused to hold a press conference to discuss his performance. Instead, he tweeted about it.

Modi has become the world's No. 2 most popular politician in the Twittersphere after U.S. President Barack Obama, with more than 18 million followers. The way he has used social media to build up his image and communicate with voters is the focus of a new study by a team of researchers led by Joyojeet Pal, who analyzed more than 6,000 tweets by Modi over a five-year period.

"Thoughtful construction of messages on Twitter has helped Modi build a powerful online brand, allowing him to overcome a problematic past and emerge as a techno-savvy global leader who speaks directly to his electorate," said Pal, assistant professor in the School of Information at the University of Michigan.

The best examples of Modi's well-crafted tweets include his most popular one: "India has won," posted May 16, 2014, when his party was victorious in the general elections. It remains the most retweeted message in the history of Twitter in India.

On India's Independence Day last year, Modi tweeted: "Let new Start-Ups emerge in every part of India. India must become No.1 in Start-Ups. Start-Up India, Stand Up India" with a video link to his speech.

When he visited rival Pakistan, Modi broke the news of the surprise trip on Twitter. He also tweeted congratulations to the Indian cricket team on its World Cup win and thanked the White House after his U.S. visit.

Modi's social media image has become all the more important because he has virtually shunned traditional media. Yet, he comes across as the most interactive prime minister India has ever had.

"If you want to listen to Modi, please go to his social media feed—whether you are a citizen, a print reporter or a television channel," said Pal, whose study is published in Economic and Political Weekly. "The social media feed has become the primary source for the prime minister's opinions."

Pal added that India is not like the U.S. where the head of government is expected to routinely show up at a news conference. By using his own social media for messaging, Modi has been able to control his message, creating positive, noncontroversial tweets.

The study divides the five-year-period from 2009 to 2014 into four phases:

• Early tweets
• Elections in the western state of Gujarat
• National elections
• Prime ministry

During the state and national campaigns, Modi's account was more about his political vision. He mentioned events, took digs at the opposition party and even posted pictures with celebrities from regions where he was lacking large support.

"On September 13, 2013, his birthday, his account suddenly followed a number of his most active followers. This remains the only time when Modi followed a number of people," Pal said, adding that it was seen as a call to action. Those he followed immediately changed their profiles to Modi's face and pushed his campaign forward.

The research also points out a fundamental change in the way the ruling Bharatiya Janata Party campaigned in the last elections with Modi at the helm.

"Traditionally, BJP has had a strong party philosophy," Pal said. "The leader, however strong, remains secondary to the lotus, the symbol of the party. In this election, the entire social media discussion was about Modi rather than about the party."

A good example of this is the #SelfieWithModi campaign, Pal added. People took selfies at voting booths with cutouts of Modi showing the black voting ink mark on their finger and using the hashtag to post the pictures.This innovative way of using the hashtag let followers feel a sense of direct participation and contribution to the leader's initiative, a unique use of Twitter by a political leader.

As prime minister, almost every tweet posted on the @narendramodi handle has been retweeted and favorited at least 1,000 times.

"As the leader of India, his tone has changed to that of a benevolent ruler more congratulatory, and worded to inspire. Retweeting this is seen as a celebration of India," Pal said.