Sen. John McCain, the presumptive Republican nominee for president, lands in Iraq on Sunday, set to meet with Prime Minister Nouri al-Maliki, Gen. David Petraeus and, of course, U.S. troops as part of a fact-finding trip by the Senate Armed Services Committee.Meanwhile, Sens. Hillary Clinton and Barack Obama are still battling for the Democratic nomination for president, questioning each other's experience, judgment and ability to lead the nation in increasingly heated tones. As the Democratic primary season drags on, McCain is seeking to position himself as a world leader, allowing him to show off his knowledge of foreign and military affairs.