Julian Zelizer, a history professor at Princeton University, is the author of “Jimmy Carter” and the editor of “The Presidency of George W. Bush.”

At key moments in his presidency, Barack Obama has struggled to win the support of the American people through the power of his oratory. The power of persuasion has traditionally been one of the most powerful weapons of the commander in chief.

On Wednesday, in his most recent effort to recreate the power of the bully pulpit in the modern age of communication, the president conducted a town hall tweet session on the White House Twitter account, which enjoys more than 2 million followers. This is the latest effort in a series of attempts to use social media, such his Facebook town hall, to communicate to the American people.

Thus far, however, President Obama has had trouble taking his case directly to the public. This is ironic and puzzling since he was the candidate who dazzled Americans during the 2008 campaign, including many Republicans.

How can this be? Throughout the 20th century, presidents used the bully pulpit to win public support. President Theodore Roosevelt courted reporters and delivered major speeches, covered by most of the newspapers, on key legislation such as railroad regulation and food inspection....