The green light Ehud Olmert recently gave to Kadima party primaries marks the beginning of the end of the Olmert era. The buildup to the primaries will also revive the debate that consumed Israelis in 2005 and 2006 about the viability, relevance, and value of a centrist party. In my new book, Leading from the Center: Why Moderates Make the Best Presidents, which I am launching this week, I argue that centrism is a traditional - and essential - way of governing in the United States. Israel, too, would flourish with prime ministers leading from the center, although the moderate impulse in Israel is weaker than in the United States. The discussion about American centrism, like so many discussions about American politics, dates back to the Founding Fathers, who established the country. As children of the Enlightenment, the Framers trusted reason and feared partisanship. They hoped America would be led by presidents who were philosopher-kings, floating above the political fray, hewing to what George Washington called the "middle way," advancing our "common cause." As America's first president, Washington played a more realistic political game than the Founders expected. Still, Washington spent much of his presidency urging subordinates and citizens to be reasonable, to learn to disagree without being disagreeable, and to follow a moderate path of civility and rationality in political discussion and actual governance. Even as parties developed, America's governing structure as well as its founding philosophies pushed politics toward the center. With no proportional representation, and "winner take all" elections giving victors full power, the system encouraged the formation of two parties. Both parties tried to forge broad national umbrella organizations, uniting north and south, east and west. Power was not shared but concentrated, especially on the presidential level. Quite simply, parties needed the votes, they needed the mythical 50 percent plus one, a majority in the Electoral College, to assume power. EVEN ONCE elected, America's greatest presidents succeeded by leading from the center. Abraham Lincoln was a pragmatist who saved the union by striking a delicate balance between Northerners committed to abolishing slavery and Northerners more passionate about preserving the union. Theodore Roosevelt taught that romantic nationalism could be the glue holding a centrist vision - and party - together. With his step-by-step incremental reforms, Franklin Roosevelt maneuvered deftly between radicals demanding revolution and businessmen defending the status quo to improvise the New Deal. More recently, Ronald Reagan understood that if he governed from the right, he would fail, but if he veered toward the center while keeping certain core principles, he could restore American patriotism while reviving America's economy. AMERICAN HISTORY teaches us that not all plays to the center succeed. Both Richard Nixon and Jimmy Carter had surprisingly moderate policies, but each of their presidencies foundered for other reasons. In Nixon's case, his anger and illegal acts did him in; in Carter's case his pessimism and incompetence did it. Bill Clinton was also a moderate, but he was a spineless centrist, far too willing to sacrifice core ideals. Had Clinton fought as hard for some policies as he did to keep his presidency during the Monica Lewinsky scandal, he might have fulfilled his potential, rather than being remembered as a disappointing "woulda, shoulda, coulda" president. America's experience teaches that democracies need a muscular moderate, virtuous enough to stick to defining principles, nimble enough to adapt to the unpredictable circumstances any leader faces. Democracies require civility, tolerance, mutual appreciation of rights and liberties, to thrive. Just as Al Gore has taught us to measure our own carbon footprints, we need to assess a leader's toxic footprint. A leader who leaves a democracy more divided, more cynical, more mistrustful, has failed. ISRAEL LACKS America's historically consecrated moderate tradition, but shares America's need for national unity and mass civility. We often forget that Israel's governing structures were established by Eastern Europeans emerging from autocracy and that the bulk of Israel's population consists of Middle Eastern and North African Jews new to democracy. The Zionist revolution was not a centrist revolution like the American Revolution, and the resulting Israeli political parties were more ideological, narrow, and fragmented than the American parties. Israel's founders, such as David Ben-Gurion and Menachem Begin, came from warring ideological camps. To this day, the Knesset includes a dizzying array of parties, some of which question the state's core ideals. WHEN ARIEL Sharon founded Kadima, he was trying to advance his career, not to trigger a much-needed democratic reform or push toward civility. Wherever one stands on the question of the disengagement from Gaza, there is no doubt that Sharon bulldozed over democratic norms to impose the plan on his reluctant party and on his constituents. He posed the question in various forums, repeatedly ignoring the "no" answer he received. Sharon's successor Ehud Olmert has continued to give centrism a bad name, revealing a Clintonesque tendency to maneuver constantly to stay in power and appearing more committed to staying alive politically than leading the country effectively, let alone morally. Still, Sharon's and Olmert's Kadima party has provided an infrastructure for a badly needed push toward the center. Israeli politics does not only need to be cleansed of corruption, a new civility needs to take hold among the leaders and the led. Israelis should start worrying about their leaders' toxic footprints - and their own. A democracy needs a sense of mutuality, unity, tolerance. Too often those ideals are mocked not just violated in Israel. Israelis have long displayed national unity during times of war - and in pursuit of peace. Israel needs - and deserves - a leader who can summon that same sense of national unity and fraternity to help make the country thrive day-to-day, not just survive during crisis. The writer, a professor of history at McGill University, is the author of Why I Am a Zionist: Israel, Jewish Identity and the Challenges of Today. His next book, Leading from the Center: Why Moderates Make the Best Presidents, has just been released by Basic Books.