The survey, commissioned by CNN and conducted May 29-31 by ORC International, said 54 percent of respondents favored marriage between gay and lesbian couples, with 42 percent opposed. Three-quarters of both supporters and opponents said they felt strongly about their position.
The poll noted a partisan divide, with seven in 10 Democrats, and six in 10 independents, saying same-sex marriages should be recognized as valid by the law. Republicans were 72 percent opposed.
It also pointed out a generational divide. Nearly two-thirds of respondents under age 50 supported legal same-sex marriages, and 55 percent of those over 50 were opposed.
The telephone poll sought the opinion of 1,009 adults nationwide, and had a sampling error margin of plus or minus 3.5 percentage points, CNN said.