Republican presidential candidate John McCain is making his sixth trip to Iraq this week. The four-term Arizona senator, who supports the war and President George W. Bush's troop buildup strategy, plans to spend the July 4 Independence Day holiday with US troops. He has visited the war zone every three months over the past year. McCain, the top Republican on the Senate Armed Services Committee, has become closely linked to the war. He has planted himself firmly on the side of the president he hopes to succeed and the three in four Republicans who still view the war as a worthy cause. Most people in the United States, however, call it a hopeless effort.