A breathless nation awaits. Or does it?

President Barack Obama sits at his desk after addressing the nation about the BP oil spill from the Oval Office of the White House in Washington June 15, 2010. (REUTERS/Kevin Lamarque)

There was a time when a presidential speech to the nation was a moment of high drama — when most Americans gathered around their radios or televisions to hear words of great consequence.

When President Franklin Roosevelt spoke, Doris Kearns Goodwin noted in her book “No Ordinary Time,” you could walk through a neighborhood and hear every word of his talk through the windows of every home. When President John F. Kennedy announced a U.S. embargo on Soviet ships during the Cuban Missile Crisis of 1962, and when President Richard Nixon appealed to “the great silent majority” to support his Vietnam policy in the fall of 1969, there was a sense that big matters were at stake.

President Barack Obama’s speech to the nation Tuesday night is not one of those times.

Indeed, if the subject at hand were not the murderous use of chemical weapons against civilians in Syria, there would be something comic about the setting for the speech.

For openers, the premise of the speech has been upended in the last 24 hours, in large measure by an off-hand comment by Secretary of State John Kerry about a possible resolution — international control of Syria’s chemical weapons stockpile — that, in Kerry’s own words, “can’t be done.”

But the Russian government seized on Kerry's words, proposing a plan to avert U.S. military action in Syria by placing its chemical arsenal under U.N control. Obama and some members of Congress seem open to the idea.

So the core message that Obama was going to deliver — that we must hold Syria accountable for an atrocity that even Hitler and Stalin did not commit — will now be forced to reflect the fact that there may be a diplomatic solution to the crisis, even as Obama will insist his threat of military force is what brought it about.

What makes Obama’s speech far less portentous than those of other presidents, however, is not just the specifics of the Syrian dilemma. It goes to the heart of the power of a president to persuade.

Put a president in front of the cameras and behind the desk in the Oval Office, and almost instantly talk begins about “the bully pulpit” — Theodore Roosevelt’s phrase for the power of the chief executive to summon support from the citizenry. It’s a power that has always been exaggerated, as historian George Edwards III convincingly demonstrates in his book "On Deaf Ears." And at a time when the prospective television audience has been fragmented by so many alternatives, the president’s power has been structurally diminished as well.

Similarly, the idea that political leaders and citizens rally behind a president on international matters has always been overstated. Politics has often not “stopped at the water’s edge.”

Republicans sharply attacked FDR’s conduct of World War II in 1942 and 1944 and President Harry Truman’s conduct of the Korean conflict in 1952. Nixon’s Democratic challenger in 1972, South Dakota Sen. George McGovern, sharply criticized Nixon’s Vietnam policies, and both Kerry and Obama made the Iraq War a central issue in the 2004 and 2008 presidential campaigns against President George W. Bush.

Then there's the fact that two generations in Congress have found themselves misled by White Houses during the Vietnam escalation and then the run-up to the Iraq War, and are simply unwilling to give this White House the benefit of the doubt. That skepticism is compounded by the refusal of many, if not most, House Republicans to support anything Obama advocates, and the strong anti-war disposition of most congressional Democrats.

Barack Obama came to national prominence on the power of his rhetoric. That power has never faced a test as daunting as it confronts tonight.