While 57 percent oppose granting such marriages legal status, 40 percent favored doing so, results of the poll released Wednesday indicated, showing little change from a poll taken a year ago.
While support for legal same-sex marriage is higher now than when Gallup first asked about it in 1996, support appears to have stalled in recent years after peaking at 46 percent in 2007, the Princeton, N.J., polling agency said.
Self-identified liberals demonstrated the greatest support for legal gay marriage at 75 percent in the recent poll, Gallup said. Only 19 percent of conservatives said they thought same-sex marriages should be legally valid.
Fifty-five percent of Democrats said they approved of same-sex marriages, compared to 45 percent of independents and 20 percent of Republicans.
Forty-eight percent of Americas said allowing legal same-sex marriages would change society for the worse, more than three times the 13 percent of respondents who said they believe legal gay marriage would change society for the better. The remaining 38 percent say it would have no effect on society or did not have an opinion, Gallup said.
Results are based on telephone interviews with 1,015 adults conducted May 7-10. The margin of error is 3 percentage points.