The results indicated Obama had a 4 percentage point advantage over Romney among non-veterans.
Romney leads by 1 percentage point among non-veteran men, while holding a 28 percentage point bulge among male veterans.
Overall, Obama and Romney are tied at 46 percent each among all registered voters in the latest Gallup survey.
About 24 percent of all U.S. men are veterans while 2 percent of U.S. women are vets, the Princeton, N.J., polling agency said. The percentage of female veterans didn't differ significantly in their presidential preference from the vast majority of women who are not veterans.
Results are based on nationwide telephone interviews with a random sample of 43,352 adults conducted as part of Gallup Daily tracking April 11-May 24. The margin of error is 1 percentage point.