Moments after tramping out of my building’s swaying stairwell and into the street during August’s D.C. earthquake, I checked my phone’s Twitter app and got my first good postquake laugh. Salon’s Alex Pareene cracked: “I think Chris Christie just jumped into the race.”

It’s not clear yet whether he will or won’t, but one of the most-discussed issues in the current Christie, er, “boomlet” is whether the New Jersey governor is “too fat to be president.”

If we’re casting a romantic comedy, we’d want someone built more like Matthew McConaughey, but since we’re picking a president here, we could stand to focus on Christie’s ideas.

The governor’s speech at the Reagan Library last week, on American exceptionalism, provided good insight into how the governor thinks about America’s role in the world.

American exceptionalism once stood for the proposition that America had developed a unique political culture of “liberty, egalitarianism, individualism, populism, and laissez-faire,” (as sociologist Seymour Martin Lipset put it) that served as an example for the world.

Lately, alas, the phrase has become shorthand for jingoism, bombast and national self-flattery. It’s turned from justifiable pride in our country’s uniqueness to something more bellicose and juvenile: “My dad can beat up your dad.”

You can see this in the manufactured outrage over President Obama’s 2009 comments to a foreign reporter: “I believe in American exceptionalism, just as I suspect that the Brits believe in British exceptionalism and the Greeks believe in Greek exceptionalism.”

Now, whatever those countries’ current difficulties, the British did invent the common law, and the Greeks came up with philosophy and drama, so maybe we can permit them their dram of national pride. It’s not a zero-sum game.

Yet in his book Fed Up! Texas Gov. Rick Perry lambastes Obama for suggesting as much: “You got the first half right, Mr. President,” he snarls.

Perry actually seems concerned that people will think he’s unpatriotic for criticizing the federal government: “Now, do not misunderstand me. America is great.” Perry’s rival, Mitt Romney, played it safe, calling his campaign book No Apology: The Case for America’s Greatness.

There’s something a little desperate and insecure about this competition to see who can bray the loudest at proclaiming our greatness.

At the Reagan Library, Christie refused to play along. American exceptionalism, he argued, “must be demonstrated, not just asserted.”

Christie emphasized reform at home, America living up to its free-market, limited-government principles, to better serve as “a beacon of hope for the world.”

In Christie’s formulation, austerity is, in a way, a “forward strategy of freedom,” minus the bombs and bloodshed. Solving our entitlements crisis at home is a way to enhance our influence abroad.

Of the ongoing Arab revolutions, Christie argued: “There is no better way to reinforce the likelihood that others in the world will opt for more open societies and economies than to demonstrate that our own system is working.”

There’s nothing in the speech to suggest that it’s America’s role to democratize other nations at gunpoint. He closes with Reagan’s invocation of John Winthrop: America is “a city on a hill” that leads the world mainly by force of example.

Christie has never been accused of being subtle, but you can read the speech as a subtle rebuke to neoconservatives and armed humanitarians on the left.

A Christie-Obama race would pit our lean, ambitious president — who’s proven so profligate with American blood and treasure — against this brash bulky figure, arguing that we need to check our appetites and tighten our belts.

That would make for an interesting contrast and an instructive debate.