Why are U.S. politicians slow to respond as Missouri simmers?

David Shribman, executive editor of the Pittsburgh Post-Gazette, won a Pulitzer Prize for coverage of U.S. politics.

Missouri is known in American folklore as the "show-me state," a shorthand to describe a people who take nothing on faith but instead insist that those making assertions must "show me" the evidence .

Right now the "show-me state" is showing an ugly face to the world, which might be why, Thursday morning, the state's Democratic governor, Jay Nixon, cancelled a visit to the State Fair and hurried to Ferguson, the site of anger and violence following the slaying of an unarmed black teenager by a local police officer.

Later Thursday, President Barack Obama chimed in with an appeal for "peace and calm on the streets of Ferguson." Until then, the sound you hardly heard amid the tumult in the troubled suburb of St. Louis was the drone of political figures raising their voices.

There was plenty of other noise coming from that embattled community, and most of it expressed the deep despair of a community convulsed in rage. We know the name of the young man (Michael Brown) but until a hacker group said it unearthed his identity, we had no clue of the name of the police officer who killed him and who now is on leave from the force. That, plus the appearance of gun-toting police in military kit, only inflamed an incendiary situation that already included looting and vandalism.

Until President Obama spoke up at Thursday from his island retreat to deplore the use of force in Ferguson and call for an investigation, there had been only the (perfunctory) politicians' expressions of concern and appeals for calm.

Only now, as the upheaval approaches its sixth day, are there constructive words being uttered and gestures made in response to a one of those signature American episodes that train the eye, and the conscience, to the country's troubled legacy of racial strife. Some came from two potential Republican presidential candidates, Senators Rand Paul of Kentucky and Ted Cruz of Texas. Mr. Paul, in an essay for the TIME website, said the "outrage in Ferguson is understandable" and added: "If I had been told to get out of the street as a teenager, there would have been a distinct possibility that I might have smarted off. But, I wouldn't have expected to be shot."

"While Ferguson, with its farmers' market and its seven-month "citywalk" concert series, might on the surface be a symbol of racial integration – about 6,000 whites living amid about 14,000 blacks – there are tensions beneath that surface, with blacks disproportionately targeted by police, according to a 2013 state study.

Indeed, now the city is emerging as a symbol of discord and tragedy.

But there is larger symbolism involved. Missouri entered the Union as part of a landmark 1820 compromise that approved the admission of the state, which permitted slavery, into the country as part of a balancing act that also approved the admission of Maine, a free state. The state played a role in the Dred Scott case of 1857 that was one of the preludes to the Civil War.

Two-thirds of a century ago, the great American writer John Gunther wrote a landmark book about the United States called Inside U.S.A. and the second sentence of his chapter on Missouri reads this way: "Here...you will find almost every American problem in peppery miniature." This week's crisis only underscores that truth.

Mr. Obama was briefed on the situation at his holiday hideway on Martha's Vineyard off the Massachusetts coast and through Thursday morning had only issued a relatively bland statement, calling for Americans to "comfort each other and talk with one another in a way that heals, not in a way that wounds." But the White House, sensitive about the prominence of the president's attendance at a Martha's Vineyard social event while Ferguson was in upheaval, moved Thursday to take a higher profile as events unfolded.

Mr. Obama's predecessor, George W. Bush, was broadly criticized for a "fly-over" visit to the Southern areas ravaged by Hurricane Katrina in 2005 – an act he later described as a "huge mistake." But in fairness to Mr. Bush, and to Mr. Obama, both presidents have wondered whether high-profile journeys to crisis areas designed to offer comfort instead only serve to distract emergency personnel's attention from their work to ameliorate those calamities.

Right now many of America's politicians are, like the president, on vacation. This week's events are a reminder that in the United States racial tension seldom takes a holiday.