WASHINGTON — Barack Obama, the first commander in chief to regularly send emails and to use Twitter and Facebook, has added another breakthrough to his technological legacy: first president of the United States to use Snapchat.

He recently took time out from a packed schedule of campaign events for Hillary Clinton to record an interview for Snapchat, part of a push to galvanize support for Mrs. Clinton among millennials.

The result resembles nothing so much as an advertisement for Mrs. Clinton, targeted at the young people whose enthusiastic backing propelled Mr. Obama to office but whose enthusiasm for his chosen successor has been more tempered. Democratic strategists have worried that younger voters, turned off by the bitter tenor of the race and more challenging than older voters to turn out even in the best of times, may not bother to vote for her.

“She’s fought on behalf of people who really need somebody to fight for them — that should be inspiring enough,” Mr. Obama told Peter Hamby, the host of Snapchat’s political show, “Good Luck America.” (The show is accessible through the Snapchat Discover section, which will make the episode featuring Mr. Obama available for 48 hours, beginning at 6 a.m. Eastern time on Tuesday.)