On the heels of his highly publicized Cuban visit, former President Jimmy Carter has again demonstrated his willingness to leapfrog diplomatic niceties in an effort to accelerate history. It is, by any account, the latest chapter in a remarkable post-presidency.

Through the work of the Carter Center in Atlanta, with its emphasis on human rights, Third World development, electoral monitoring and health issues largely neglected by other statesmen, Carter has come closer than anyone before him to institutionalizing the ex-presidency. In the quarter century since leaving the White House, he has written more books, visited more hotspots, and discomforted more of his successors than any ex-president since Herbert Hoover.

Another one-term chief executive with an unrelenting work ethic and a moralistic temperament ill-suited to political gamesmanship, Hoover predated Carter’s faith-based humanitarianism. Abandoning his lucrative engineering career at the age of 40, the Iowa blacksmith’s son would go on to feed a billion people in more than 50 countries.

In February 1938, a generation after coming to Belgium’s rescue during World War I, Hoover returned to a continent flirting with suicide. Not all his friends thought the trip well-advised. To begin with, there was Hoover’s obvious antipathy, returned with compound interest, toward the Roosevelt White House. Warned that he would be expected to join in toasts to the president of the United States, Hoover said that presented no problem. But what if the former president, on foreign soil, was asked to defend Roosevelt’s European policies?

“I think I can keep silent in seven languages,” replied Hoover.

In the event, the children of 1914-18 turned out en masse to honor the man they called Onkel Hoover. An unscheduled Berlin meeting with Adolph Hitler left the American visitor shaking his head over purple-faced outbursts occasioned by the mention of the words Jew or democracy. Afterward Hoover confided to a friend that an American jury would find the leader of the Third Reich insane. Though passionately resolved that his own nation should avoid Europe’s murderous quarrels, Hoover was careful to observe the restraints traditionally visited upon former presidents when traveling abroad.

No sooner had he returned home, however, than Hoover threw himself into the war to avert war. His verbal assault on Roosevelt’s course in the penultimate days leading up to Pearl Harbor was unrelenting. He did not hesitate to draw upon his European experiences, yet Hoover’s public criticism of the White House was reserved for American audiences. Perhaps he remembered Henry Ford’s seriocomic Peace Ship, one of the more harebrained episodes in a life generously endowed with foolishness. Whatever the reason, Hoover did not confuse his former office with his current status.

Sixty years later, the issue raised by Carter’s latest mission, a natural sequel to his earlier interventions in Haiti, Bosnia, and the Korean peninsula, is less one of political awkwardness than of constitutional confusion. Carter’s defenders can argue that, just as his willingness a decade ago to publicly embrace Yasser Arafat foreshadowed a mere evenhanded U.S. approval to the Middle East, so his recent discussions with Fidel Castro have usefully rekindled the smoldering debate over American policy toward Castro’s Cuba. If the pope can visit Cuba, why not a former American president?

But of course, the pope is the undisputed, reigning head of a church for which he speaks with absolute authority. Put Cuba aside for the moment. Imagine the popular and press reaction if a conservative former president, fearful that a successor’s commitment to arms control might leave the Untied States vulnerable to nuclear blackmail, were to journey to Moscow for meetings with Russian nationalists or Soviet-era hardliners. Worse, imagine an involuntarily retired leader whose disagreement with a successor’s military and diplomatic policies goads him, on the eve of war, to attempt to frustrate those policies.

It has happened before. In November 1990, following Saddam Hussein’s rape of Kuwait, a freelancing Carter appealed to world leaders for an Arab solution to the crisis, one that would simultaneously “at long last also force Israel to withdraw from the occupied territories.” Even as the Bush White House struggled to assemble and maintain a broadbased coalition to defeat Saddam’s aggression, Carter, in what his most recent biographer calls an “astonishing act,” urged the leaders of Egypt, Syria and Saudi Arabia to break with Washington. For good measure, the former president wrote anti-war senators, who mustered 47 votes in opposition to the use of force against Iraq.

When the full extent of his activities became public some three years later, even Carter’s admirers were appalled. “Breathtakingly brazen,” said one normally friendly journalist. “Former presidents, of all people, do not have their own foreign policies,” he added. The message does not seem to have permeated the walls of the Carter Center. To be sure, while in Cuba, Carter was careful to balance his criticism of the U.S. trade embargo with calls for greater democracy in that outpost of palm-fringed Stalinism. Ironically, his visit coincided with Bill Clinton’s attendance at East Timor’s independence celebrations. Clinton was there at the behest of the Bush administration, which was no doubt grateful for a former president who is willing to practice a more traditional brand of diplomacy.

If, as historian Douglas Brinkley contends, Carter’s is the unfinished presidency, someone had better tell the Founders. The question remains: What does a relatively young ex-president do to fill his time, consolidate his reputation, or vindicate his administration? In the wake of his humiliating third-place finish in the 1912 election, a mellow William Howard Taft claimed a unique distinction. Never, said Taft, had any American been so overwhelmingly elected ex-president. Taft went on to enjoy a distinguished post-White House career, in the course of which he regained the respect and affection of his countrymen.

But he did so from the cloistered precincts of the judiciary. Few occupants of the White House have so judicious a temperament. If they did, they wouldn’t reach the White House.

For now, the Carter model is in the ascendancy. Soon Bill Clinton will open his own presidential library in Little Rock, joined to an ambitious policy institute plainly inspired by the Carter Center. With a whole world to work on, and no shortage of historians to convert, one can only hope that the famously activist Clinton will not take his lack of official responsibility as a license to be irresponsible.

Richard Norton Smith is a nationally recognized authority on the American presidency and a regular commentator on C-Span and “The News Hour with Jim Lehrer.” He has written numerous books on American history and national political figures and has served as director for the presidential libraries of Herbert Hoover, Dwight D. Eisenhower, Ronald Reagan and Gerald Ford. He now is director of the new Robert J. Dole Institute of Politics at Kansas University.