The poll was conducted by a journalism professor at Northwestern University in Evanston, Ill., and Ipsos Public Affairs, the university said. USA Today joined in the project.
Ellen Shearer, the professor, said non-voters tend to be younger and less educated than voters. While 26 percent described themselves as Democrats and 15 percent as Republicans, 32 percent said they were independents. Another 13 percent identified with another party and 14 percent said they identified with no political party.
Almost half said they favored Obama and 26 percent Romney.
Shearer identified six types of non-voter. She said 27 percent are "pessimists," older white men who are skeptical of government and tend to be conservative, and 20 percent are "too busys," older women who support big government.
Chester Orgeron, 48, of Ponchatoula, La., a pessimist, told USA Today: "I'm just disappointed in the job that Obama has done, and I don't think Mitt Romney could have done any better."
The "strugglers," 19 percent of non-voters, are younger women with little education and low incomes. "Tuned outs," 16 percent, are young people with little interest in current affairs.
About 11 percent of non-voters are "active faithfuls," who are generally from the south and relatively high income. The group includes both whites and blacks but few Hispanics or Asians, and many say they do not vote for religious reasons or because they do not like either candidate.
The smallest group, "doers," are 8 percent of non-voters. They are generally young Hispanic men who keep track of what is going on in the world and say they do not vote for logistical reasons.
The poll surveyed 1,686 U.S. citizens who were at least 18, including 516 who voted in the presidential election and 1,170 who stayed home. The margin of error is 4.9 percentage points for voters and 3.3 points for non-voters.
The project, Non-voters in America, has a website, www.nonvotersinamerica.com.