Barack Obama has begun, finally and reasonably firmly, to clarify his stance regarding the scope and character of the ongoing U.S. role in Iraq. In so doing, the senator from Illinois has imposed clarity on a race for the presidency that, while it certainly is not a single-issue contest, will always at its most fundamental level be about the question of whether America is going to elect a president who plans to end the war or who intends to manage it.

The presumptive Democratic nominee for president says that on his first day in office he will begin the process of extracting U.S. troops from Iraq so that they — and the United States — can get serious about combating terrorism.

Noting Prime Minister Nuri al-Maliki’s request for a withdrawal timetable, Obama explained in a much-anticipated speech Tuesday that “now is the time for a responsible redeployment of our combat troops that pushes Iraq’s leaders toward a political solution, rebuilds our military, and refocuses on Afghanistan and our broader security interests.”

Of course, the presumptive Republican nominee for president cut Obama no slack. Unlike his rival, John McCain says — with an odd combination of bluster and vagueness — that he’s against an exit strategy because, “I know how to win wars.”

The difference between Obama and McCain, we are told, comes down to this:

The Democrat who would be president has set a serious strategy for bringing the war (or “police action” or “occupation” or “major presence” or whatever you want to call it) in Iraq to a relatively rapid conclusion, even if that conclusion is imperfect and open to criticism. That strategy is flexible — perhaps more flexible than some of the candidate’s more ardent supporters would like — but it is real and it is likely to be implemented along a schedule that would begin with his inauguration on January 20, 2009.

The Republican who would be president absolutely rejects any strategy that is defined by the American people or their representatives in Washington for bringing the war (or “police action” or “occupation” or “major presence” or whatever you want to call it) to the conclusion that Obama proposes. Only “events on the ground” in a country that – despite McCain’s hysterically-inflated fantasies about the “success” of his beloved “surge” — has seen little progress toward the sort of long-term political, ethnic and social stability that might make for an easy exit will determine McCain’s schedule.

This distinction is best understood as a clash between the approaches of two presidents who inherited unpopular wars.

Obama is an Eisenhower man. Dwight Eisenhower, who had served as Supreme Commander of the Allied forces in Europe during World War II, campaigned for president in 1952, when the United States was mired in the quagmire that was the Korean War. Ike’s promise during that campaign was to “go to Korea” and end the war. Upon his election, that is what he did.

McCain is a Nixon man. Richard Nixon, who had served as a supply clerk and enjoyed some success as a poker player during World War II, campaigned for president in 1968, when the United States was mired in the quagmire that was the Vietnam War. Tricky Dick refused to be pinned down regarding timelines or strategies for addressing the mess in Vietnam, suggesting simply that “new leadership will end the war and win the peace in the Pacific.” So vague was Nixon that his Democratic opponent in the race, Hubert Humphrey, suggested that the Republican must have a “secret plan” regarding the war. As it turned out, Nixon’s plan was to keep the war going. Unlike Eisenhower, who stopped the killing, Nixon, guided by “events on the ground,” illegally expanded the undeclared war from Vietnam into Cambodia and Laos. Tens of thousands of Americans and hundreds of thousands of southeast Asians died before the fighting finally wound down a half decade after the Republican’s election.

Non-defensive wars end not when circumstances “on the ground” in distant lands dictate but when presidents who choose to be leaders rather than managers of misery decide to end them.

Barack Obama, like Dwight Eisenhower, proposes to be a leader.

John McCain, like Richard Nixon, proposes to be a manager of misery — and the American decline that will hasten with each passing year of the quagmire in Iraq.