Washington state Senator Jim Kastama on Thursday announced he would support an effort to make Washington the seventh state to legalize gay marriage, the AP reported.

Kastama's support puts the proposed legislation just one vote shy of passage in the Senate.

“This decision is a deeply personal one,” he said in a statement. “Unlike some of my colleagues in liberal districts, I will not return home to cheers and handshakes. I represent the district I was raised in. My wife and I purchased and live in the same house I grew up in and we have raised our family there. My district has known me my whole life and for 16 years has entrusted me to be a fiercely independent legislator. The people of my district are generous and decent, but I also know that there are childhood friends who will never forgive me for this vote.”

Kastama, a candidate for secretary of state, said that marriage laws need to evolve to mirror a shift in society. The position is a reversal for Kastama, a conservative Democrat, who in 1998 voted in favor of a bill which defines marriage as a heterosexual union. However, he supported a 2009 expansion to the state's domestic partnership law which gave gay and lesbian couples all the protections of marriage.

The measure is expected to clear the House with ease and Governor Chris Gregoire pledged her support during a press conference earlier this month.

Five other senators say they remain undecided on how they'll vote on the proposed legislation, including two Republicans.

The House and Senate have scheduled hearings on the bill for Monday.

Currently six states – New York, Massachusetts, Iowa, Connecticut, Vermont and New Hampshire – and the District of Columbia have legalized gay marriage. Gay marriage bills have also been filed in Maryland and New Jersey, which currently recognizes gay couples with civil unions.

(Related: NOM pledges to work against Washington state Republicans who support gay marriage.)