A majority of Americans surveyed believe dropping atomic bombs on Japan during World War II was the right thing to do, but support was weaker among Democrats, women, younger voters and minority voters, according to a Quinnipiac University poll.

The poll, released Tuesday, found 61 percent of the more than 2,400 American voters questioned believe the U.S. did the right thing. Twenty-two percent called it wrong and 16 percent were undecided.

The first bomb was dropped Aug. 6, 1945, on Hiroshima. An estimated 140,000 people were killed instantly or died within a few months. Tens of thousands more died from radiation poisoning in the years following.

Three days later, another bomb was dropped on Nagasaki, killing about 80,000 people. Japan surrendered less than a week later.

"Sixty-four years after the dawn of the atomic age, one in five Americans think President Harry Truman made a mistake dropping the bomb," said Peter A. Brown, assistant director of the Quinnipiac University Polling Institute.

The poll asked a single question: "Do you think the United States did the right thing or the wrong thing by dropping the atomic bomb on Hiroshima and Nagasaki?"