The second president he challenged was Mr Reagan. He did so in anticipation of the president's visit with Chancellor Kohl to the German military cemetery at Bitburg. The media had discovered that Waffen SS were among those buried at Bitburg. It was incomprehensible to Mr Wiesel that an American president would lay a wreath at a ceremony where those directly associated with the Holocaust were buried.
Fortuitously, Mr Wiesel was scheduled to receive the Congressional Gold Medal from Mr Reagan just prior to his departure. With the world media present, Mr Wiesel turned to a sitting president and said: "Your place is not that place," he said. "Your place is with the victims."
Mr Reagan went anyway, but the Bitburg visit lasted precisely 10 minutes. He then went to Bergen Belsen, where he spent an hour.
These two incidents were striking because it is virtually unheard of for a president to be directly challenged by someone to whom they had given a presidential appointment or were about to honour.
There was another occasion on which Mr Wiesel laid down the gauntlet to a president. During the early 1990s, a series of troubling international developments gave the Holocaust an eerie relevance. In Rwanda, the Hutus murdered more than 800,000 Tutsis in around 100 days. But it was not just in Africa, where Western commentators seemed to expect such tragedies, that genocide was occurring. Mass-murder was also taking place in the heart of Europe. The Yugoslav army and Bosnian Serb paramilitary forces attacked Bosnia and engaged in a brutal array of atrocities after the Bosnian government declared independence from Yugoslavia. Eventually, 250,000 people were killed and millions were left homeless.
The fighting in the Balkans gave rise to the term, "ethnic cleansing". Introduced by the perpetrators there, it was reminiscent of the Nazi use of euphemism, such as "deportation to the east" or "Final Solution", to linguistically camouflage murder, torture, arbitrary arrest and detention, extrajudicial executions, sexual assaults, forcible removal of the civilian population, and wanton destruction of property. These horrors occurred in full view of the world's media. Suddenly, the Holocaust had become, not just history, but a prism that refracted contemporary events.
The unprecedented moral and political capital of the Holocaust was nowhere more starkly evident than at the 1993 dedication of the United States Holocaust Museum, when Mr Wiesel berated President Bill Clinton for not doing more - or anything at all - to halt the slaughter then raging in the former Yugoslavia: "Mr President, I have been [to the former Yugoslavia]. . . I cannot sleep since what I've seen. As a Jew, I am saying that we must do something to stop the bloodshed in that country."
Mr Wiesel's public challenge to this new president who had been in office less than 100 days did not precipitate an immediate change in American policy. However, according to Roy Gutman, a reporter who covered the conflict for years, it "echoed from that moment on. It rallied people in the Congress and various communities here, in the human-rights community, the policy elite in and out of Washington."
Remarkably, unlike the debate over six or 11 million and Bitburg, this time he was not challenging a president over a symbolic matter. It had no link to the Holocaust or any other direct Jewish interest. Mr Wiesel, standing in front of a museum built on federal land with the support of three presidents and with the congressional imprimatur, was using the Holocaust as a moral yardstick with which to assess America's response - or lack thereof - to a contemporary tragedy. If the Holocaust had a mythic element, it was never clearer than at that moment.
There was, however, another message implicit in Mr Wiesel's remarks. Fifty years earlier, America had turned its back on many refugees who might have been saved. The United States Holocaust Museum was focused on an event whose victims and perpetrators were not Americans and which had not happened on American soil. Nonetheless, those most directly involved in constructing it believed it belonged on the Washington Mall because it reminded visitors both of a catastrophe that was contrary to American principles and how the US had stood by, refusing to engage. It acknowledged America's own failures.
Now Mr Wiesel, building on that message, issued a foreign policy challenge: what was happening in Yugoslavia might not be a Holocaust or genocide, but that did not absolve the US from acting to halt it.
I was present at the dedication when he spoke up. No sooner had Mr Wiesel finished speaking when one of the survivors present turned to me and said with tears in his eyes: "No one has even entered the place and it's already telegraphing a message America has to hear."
Many of us have lost someone we loved. The entire world has lost voice that "spoke truth to power". Tragically, there is no replacement in sight.
