Already, pundits and political scientists have begun to parse exactly how the junior Democratic Senator from Illinois, Barack Obama, managed one of the greatest upsets in the history of US presidential politics to win the nomination. There will be county-by-county delegate maps and charts and timelines. The truth of exactly what caused the Obama insurgency to succeed so phenomenally will probably be debated over for years to come.

Today, however, It seems to me that the simplest explanation for Obama’s stunning victory is that Obama won mostly because of his unwavering opposition to the Iraq war. That set him up in direct contradiction to his rivals (Senators Hillary Clinton and John Edwards). Obama’s opposition to the Iraq war, more than any other issue, allowed him to solidify “change” early and often as his central campaign theme.

But on Jaunary 21, 2009, his first full day as President, Obama’s biggest challenge won’t be ending the war in Iraq. That challenge will be relatively simple when compared to the labyrinth that Obama will have to navigate if he is to remain a peacemonger while in the Oval Office.

Our challenge, those of us who will elect Obama, will be to hold President Obama to the promises that he made just last week: to bring peace to the Palestinians and the Israelis and to the rest of the Middle East.

Last week, speaking at the annual convention for the influential American Israel Public Affairs Committee, Obama said: “I will do everything in my power to prevent Iran from obtaining a nuclear weapon. Everything.” He added the extra “everything” to emphasize that there should be no question that he could use military action against Iran. Obama went on to describe how he’ll start with “aggressive, principled diplomacy,” but that all options were on the table.

Too many candidates for the American presidency, particularly Democrats, have been elected to the White House promising peace, then found that political pressures during their term made it impossible for them to avoid going to war.

Unlike most Democrats, when it comes to foreign policy, Obama has talked a lot about using “soft power” — diplomacy, economic carrots and sticks, and other non-military persuasion to win over non cooperative governments. Most Democrats running for president in recent years have felt that expressing anything less than a hawkish view about “American power” would be political suicide. Hence John Kerry’s bumbling prevarications on Iraq during the 2004 campaign, and hence Michael Dukakis riding around in a tank. The horrible failure of the Iraq war has changed the political calculus enough so that Obama can win both the primary and the general election on a platform of bringing the troops home. Still, to be sure, on just about every other foreign policy question, Obama feels pushed to out-hawk the Republicans (who can always be counted on for warmongering).

Senator John McCain, the presumptive Republican nominee, feels he’s found a huge opening on the issue of Iran. McCain, of course, is more than eager to start a foolish war with Iran, just as he’s been a consistent cheerleader for Bush’s Iraq war as well. Electing McCain would ensure more Bush-esque foreign policy disasters.

But McCain is convinced, wrongly, that Obama is weak on Iran, so we’ll hear more about Iran in the run up to the general election than we’ll hear about Iraq. That trend won’t stop after Inauguration Day.

For those of us who support candidate Obama today, it will be just as important to support President Obama beginning in January. President Obama will need political cover — a strong base of political support for a peace platform — in order to keep his promise to bring peace to the Palestinians and the Israelis.

Moreover, our challenge will be to organize an American movement for peace throughout the Middle East. Obama needs to know that no one wants a war with Iran, and we expect our President — elected on a platform of peace — not to wage another foolish war with yet another Middle Eastern country.