Civil War: Both sides expected the war to last no more than a few months. The Civil War necessitated conscription of able-bodied males by the Union, and prompted nationwide, violent mob action in protest. In New York City, large-scale, bloody riots raged on for four days, causing 1,000 casualties. The so-called "copperheads" opposed the Civil War, and staged some of the largest riots in American history. Widespread Northern anti-war sentiment made President Lincoln pessimistic about his prospects for re-election in 1864. Indeed, a leading copperhead (or "peace Democrat") wrote that year's Democratic Party platform. Ultimately, Lincoln won re-election when public sentiment turned around following the success of the Union Army in taking Atlanta.
Spanish-American War: The press heatedly debated this 1898 war, and the war declaration approved by Congress passed with a margin of only seven votes in the Senate. Popular support for the relatively easy fight evaporated over the controversial annexing of Spain's colonies, such as the Philippines. In 1900, Democratic presidential candidate William Jennings Bryan made his opposition to the war the centerpiece of his campaign.
World War I: In 1916, two years after the war began in Europe, President Woodrow Wilson ran for re-election as a peace candidate who "kept us out of war." Critics pounded Wilson after the U.S. entered the conflict. Opponents of America's involvement in World War I filled Madison Square Garden with their protest meetings. Those opposing the war included many Irish- and German-Americans, trade unions, socialists, pacifists and progressives who belonged to vocal radical groups. During this period there were substantial increases in these groups' membership, giving them an even more powerful voice against the war. Wilson considered existing laws insufficient to handle antiwar sentiment, and his administration used a variety of legal tools to deal with the "problem" of disloyalty -- including censorship and imprisonment. Over 250 people were convicted under the Espionage Act in less than a year.
Korean War: U.S. military involvement began in the spring of 1950 with popular support. By January 1951, however, 49 percent of Americans believed that sending troops to Korea was a mistake, and 66 percent wanted us to pull out. The war's unpopularity played an important role in the election of President Dwight D. Eisenhower, who pledged to end the war.
Vietnam War: In a 1971 public opinion poll, 71 percent called the Vietnam War a mistake, and 58 percent called the war immoral.
World War II: This stands as the sole major U.S. military conflict that had no organized block of dissenters once the Americans entered the war -- which, of course, only happened after the Japanese bombed Pearl Harbor and ushered America's entry into World War II.
This brings us to the "unpopular" Iraqi War. Bush obtained a resolution from Congress (which passed the House 296 to 133, and the Senate 77 to 23) authorizing the use of force. At the time of America's entry into Iraq in 2003, a CBS/New York Times poll found that 76 percent of Americans approved of the U.S. military action against Iraq. Even now, the majority of Americans want us to stay the course.
Aside from that, the New York Times reporter pretty much nailed it.