Support for Referendum 74, the Washington state referendum on a gay marriage law, holds an 18-point lead, according to a survey released Tuesday.

The poll was commissioned by KING 5 TV in Seattle and conducted by SurveyUSA, which interviewed 700 Washington adults in person and by telephone.

Fifty-six percent of respondents said they support keeping the law approved by legislators, while 38 percent disagree. Six percent said they were not sure.

Support has increased by six percentage points from a similar poll conducted in July. And a 7-point lead has widened to 18 points.

Support was highest among those under 34 (67%), but even a large share (43%) of seniors over 65 approve of the law.

Support among Republicans and Tea Party members was nearly even at 25 and 24 percent, respectively. A large majority (80%) of Democrats and independents (55%) support marriage equality.

Commenting on the poll, Seattle weekly The Stranger wrote: “[T]his poll may mark a gay-rights trend much larger than Washington State: This survey was conducted in the three days following the Democratic National Convention, an event marked by the country's political leaders delivering speeches embracing marriage equality as the keystone of progressive (even mainstream) ideology; the result may be a national climate shift that plays out to make 2012 the first year in US history that same-sex marriage is approved at the ballot.”