When it came to legalizing same-sex marriage in Washington, women cast the decisive votes, according to a new poll. The post-election survey conducted by Third Way, a D.C. think tank that favors gay marriage, showed women backed the marriage referendum by a whopping 15 percentage points. In contrast, men narrowly opposed the measure, by a margin of two percentage points. Overall, Referendum 74 passed by a vote of 54 percent to 46 percent. The gender gap is not surprising since other polls have shown they are more likely to support same-sex marriage. But the survey noted that the gender gap persisted in some surprising ways. For example, the gap was highly prevalent even among Democratic voters, who overall were strongly in support of the referendum. All told, 80 percent of Democratic women backed gay marriage, compared with 60 percent of Democratic men. (In contrast, Republican men and women voted about the same -- in strong opposition). The gender gap also held for voters over 50. Men in that age group opposed it by a margin of 29 percentage points while women opposed it by just 3 percentage points. The gender difference largely disappeared voters under 50, with 68 percent of women in that age group in favor compared to 65 percent of men. After Californians voted against same-sex marriage in 2008, Third Way analysts conducted research that they said showed advocates of gay marriage needed to change their message.