Voters in Washington state would keep a gay marriage law if approved by lawmakers and put up for a vote, but only with a razor thin margin, a new poll has found.

The survey of 617 registered voters was commissioned by Olympia-based KING 5 News and conducted by SurveyUSA.

When asked, “If the legislature were to approve marriage for same-sex couples, and you were asked to approve or reject the law, how would you vote?” 47 percent of respondents said they would approve the law and 46 percent said they would reject it. Seven percent refused to answer the question.

The poll, which has a margin of error of plus or minus 4 percentage points, also found that 50 percent of younger voters would approve the law compared to only 39 percent of adults over age 65.

The legislation is scheduled to get its first hearings in the House and Senate on Monday.

Opponents have vowed to force a referendum on the law, if approved by lawmakers.

The measure inched closer to passage in the Senate on Thursday with the endorsement of Senator Jim Kastama. Kastama's support put the proposed legislation just one vote shy of passage in the chamber.