His decision to speak on the terrorist threat from the Oval Office, just days after the deadly attack in San Bernardino, Calif., reflects a broad concern in the White House that the American people, distracted by the overheated cacophony of the campaign season, are not listening to him. Or at least they are not hearing what he has to say.

In the weeks since the terrorist attacks in Paris, Obama has stressed in speech after speech that U.S. law enforcement and homeland security officials are “relentless.” He has insisted the country remains “strong” and ­“resilient.” ...