And yet somehow this failed to stop al-Baghdadi’s stormtroopers lightning advance across Syria and Iraq.

WASHINGTON — As the Internet exploded recently with the story of the 14-year-old Muslim boy arrested for taking a homemade clock that was mistaken for a bomb to his school in Texas, President Obama’s small army of social media specialists wasted no time.From their office in the Eisenhower Executive Office Building, Mr. Obama’s aides determined that the president should swiftly tweet about the clockmaker, Ahmed Mohamed, whose distraught expression and handcuffed wrists were feeding a national debate about ethnic and religious profiling.

“Cool clock, Ahmed,” Mr. Obama said in a message posted on Twitter hours later from his personal account, @POTUS, to his nearly five million followers. “Want to bring it to the White House?”

Increasingly, the White House is using Mr. Obama to break news over social media. His first reaction to the Supreme Court’s ruling establishing a right to same-sex marriage nationwide in June was on Twitter, where he called the decision “a big step in our march toward equality.” He added the hashtag #LoveWins, which quickly became a trending topic. […]

“Ultimately, what all of this is about is finding ways to communicate with people in a time when media has become so disaggregated that simply communicating through the traditional means is woefully insufficient,” said Dan Pfeiffer, Mr. Obama’s former senior adviser and an architect of his digital strategy.

Social media can also be a powerful tool for burnishing the president’s image with a sometimes-fickle public. One of the most viewed postings the White House has ever shared is a YouTube video of the president taking an impromptu stroll near the White House last year, quipping “the bear is loose” as he shook hands with awe-struck tourists.

It was a time when “we were really getting beaten up, and there was no break in the narrative,” said Mr. Pfeiffer, recalling how the rise of the Islamic State was capturing public attention. “And here we had this glimpse of the president as we all wished people could see him.”