Among world leaders using Twitter, Pope Francis has the most followers, but Donald Trump is quickly gaining on him.

A study released by an organization called Burson-Marsteller says that Pope Francis has continued to increase his social media audience, but the U.S. president “has amassed millions of new followers in the past few months to become the second-most followed world leader on Twitter.”

“If his robust growth continues he is set to surpass Pope Francis to become the most followed world leader by the end of August 2017,” the study says.

The Burson-Marsteller study looks at how social media is becoming increasingly important in the world of diplomacy. It found that Twitter is the social media channel of choice for governments and foreign ministries. Facebook is the second-most popular network among government leaders and it is where they have the biggest audience, the study says.

Pope Francis moved into the number one spot for Twitter followers when Trump succeeded President Barack Obama. Obama had been “the uncontested political leader of the digital world,” the study notes:

Pope Francis (@Pontifex) has become the most followed world leader with more than 33.7 million followers on his nine language accounts. His official accounts dispense daily thoughts and prayers in 140 characters in Arabic, English, French, German, Italian, Latin, Polish, Portuguese and Spanish. U.S. President Donald Trump (@realDonaldTrump) is the second-most followed world leader, with 30.1 million followers on his personal Twitter account.

But the number of followers is only part of the story. The study also looks at followers’ interactions, such as likes and retweets, and finds that Trump is way ahead of the pope and also outshines the prime minister of India:

Over the past 12 months the @realDonaldTrump has achieved 166 million interactions, almost five times as many as Indian Prime Minister Narendra Modi, with 35 million interactions, and 12 times as many as the Turkish President and Pope Francis. His overall interaction rate (the sum of all interactions divided by the number of tweets and the average number of followers) is 0.34 percent, on par with Pope Francis.

The study also points out that Pope Francis’s two most popular tweets have to do with immigration policy and may be references to Trump’s plans to control illegal immigration, particularly that which takes place at America’s southern border. “How often in the Bible the Lord asks us to welcome migrants and foreigners, reminding us that we too are foreigners!” Francis tweeted on Feb. 18. “I invite you not to build walls but bridges, to conquer evil with good, offence with forgiveness, to live in peace with everyone,” he posted on March 18.