In the poll, 53% of American adults said they think same sex marriage should be legal, compared to 44% who said it should not be. ABC found support for same sex marriage up six points from just one year ago, when 47% of Americans told the network it should be legal, while 50% said it should remain illegal.
Support for same sex marriage has been trending up for years. In 2004, just over six in ten Americans opposed gay marriage, while about one-third supported it, according to the CNN poll.
Other pollsters have noted a similar trend. Pew Research's surveys have shown support ticking up in recent years. In a poll released earlier this month, they found support evenly split.
The issue of gay rights has long been a rallying point for conservative voters. But, as TPM has reported, some people think that has changed.
"The wedge has lost its edge," Republican strategist Mark McKinnon, who worked on Bush's 2004 campaign, told The New York Times last month.
The ABC News/Washington Post poll was conducted March 10-13 among 1,005 adults nationwide. It has a margin of error of 3.5%.