Three times in the last seven months, world leaders dissimilar in style and background have delivered remarkably similar messages to Congress and, through television, the American people. Each time, they spoke with rare eloquence, and each time they were greeted with thunderous applause and standing ovations.

In an age of ghostwriters and synthetic political appearances, here were the voices of authentic leaders speaking in original language that should have stirred America to its core. Each time, the public response was much the same: a momentary stir of excitement, then a return to personal business as usual.

And the leaders' collective message? It was to remind Americans how democratic a political system they enjoy, how powerful a symbol the United States remains in the world and how much still is expected of America in the future.

Behind their words lay a different kind of message, less explicitly expressed but nonetheless sharply put: that the United States faces a series of new challenges, and the world awaits a response as to how America chooses to meet them, if indeed it will address them at all.

To Lech Walesa, the rumpled Polish labor leader, America's challenge was to make "an investment in freedom, democracy and peace, an investment adequate to the greatness of American nation."

To Vaclav Havel, the urbane playwright president of Czechoslovakia, it was to help the world enter a new era, one "in which all of us, large and small, former slaves and former slave masters, will be able to create what your great President Lincoln called the 'family of man.' " At the same time, he said, the American challenge was also to take the lead in engendering a new sense of international responsibility "to something higher than my family, my country, my company, my success" -- a responsibility to the "the human conscience."

To Nelson Mandela, in many ways the most extraordinary of these figures, a man of such courtly dignity and formality of phrase that his grandfatherly demeanor almost masks the passion of his message, it was to remind Americans that theirs was a revolutionary nation that continues to spawn revolutionary movements around the globe.

"We could not have made an acquaintance through literature with human giants such as George Washington, Abraham Lincoln and Thomas Jefferson," he told Congress Tuesday, "and not been moved to act as they were moved to act. . . . We could not have known of your Declaration of Independence and not elected to join in the struggle to guarantee the people's life, liberty and the pursuit of happiness. . . . "

No sooner had Mandela delivered that message than his words, like his predecessors', were swiftly overtaken by old problems and sordid new ones.

The savings and loan crisis grew worse. Once again, the administration's rosy deficit projections -- a day of surplus, we were told just months ago, happily awaited us -- proved to be disastrously inaccurate. Instead of diminishing, as forecast, the deficit was soaring, triggering the latest tax-and-cut budget skirmish. President Bush's belated but welcome move on taxes notwithstanding, the deficit reduction outcome remained uncertain and, like others over the last decade, mired in partisan politics. Genuine political campaign reform languished. The legislative pace slowed amid debate about trivial, not substantive, issues.

And on the day the great South African left Washington, his behavior and character stood in sharp contrast to that of the capital's elected mayor.

Sworn testimony at Marion Barry's trial grew more squalid with each hour on the witness stand by Hazel Diane "Rasheeda" Moore. Despite damning evidence of betrayal of public trust and criminality of long standing just delivered in the courtroom, that very evening Barry was saluted by Louis Farrakhan, leader of the Nation of Islam, at a public rally attended by thousands. Farrakhan drew cheers when he called on the mayor not to step down from public life but "to run, Barry, run."

Washington's attention next shifted yesterday to the sordid, and, yes, disturbing, televised scenes of Barry and Moore in the Vista Hotel "sting."

The city and the country have far more important things to ponder. Foremost among them are the challenges issued by those admirers of America: Walesa, Havel and Mandela. America's problems, they remind us, are insignificant when measured against its ability to fulfill universal dreams. America's test, they say, is to remember what it stands for and then act on it. Is anybody listening?