After Hurricane Betsy ravaged Louisiana in 1965, President Lyndon Baines Johnson flew to New Orleans to comfort the victims. Standing in one evacuee shelter darkened by an electrical outage, LBJ shined a flashlight into his face so that his fellow Americans could see the leader of the free world who had come to bring them hope. Speaking into a megaphone, he offered encouragement to residents who had lost everything.

“My name is Lyndon Baines Johnson,” he told weary listeners. “I am your president. I am here to make sure you have the help you need.”

[Flashback, 1964: Listen to phone conversation between Sen. Russell Long and President Johnson as the senator begs for the president's help.]

Johnson knew that presidents can powerfully demonstrate what they stand for by where they stand. In standing shoulder to shoulder with citizens who had borne the brunt of a terrible storm, he let them know that in their misery, they were not alone.

Johnson’s megaphone moment is a case study in how presidents should answer the anguish of national tragedies, and it’s a lesson that leaders ignore at their peril.

Alas, there has been no megaphone moment for President Barack Obama in his response to the catastrophe plaguing south Louisiana this week. In the wake of a storm that displaced thousands and flooded huge swaths of the region, Obama continued his vacation at Martha’s Vineyard.

To his credit, the president declared a disaster for the affected areas, which should speed the flow of federal aid. He also dispatched important surrogates, FEMA director Craig Fugate and Homeland Security Secretary Jeh Johnson, to Louisiana to help.

He was right to do so, but like Johnson, Obama should recognize that leadership involves symbolism as well as substance. In times of profound need, people need to see their president up close. A president’s presence can underscore the urgency of relief efforts, goading a sluggish federal bureaucracy into action. In disasters as in so much of life, the old proverb is true: Showing up is half the game.

Presidents don’t always get these things right. President George W. Bush’s reluctance to leave his Texas ranch after Hurricane Katrina is well known, but another instructive precedent was Calvin Coolidge’s low profile after the Great Flood of 1927 submerged a large part Louisiana.

Silent Cal, so nicknamed for his reticence, should have showed up quickly back then and spoken louder.

Obama, for that matter, should have been here by now, too.