A gay couple from New Jersey is suing a group that used their engagement photo in an attack mailer against a Colorado state lawmaker who supported civil unions.

Oleksiy Maksymenko, Getty Images

The Southern Poverty Law Center says it will file a federal lawsuit Wednesday on behalf of the couple against the Virginia-based Public Advocate of the United States. The group used a photo of Brian Edwards and Tom Privitere holding hands and kissing.

The mailer questioned the values of Republican state Sen. Jean White, who faced a primary against a fellow Republican in a northwestern Colorado district. White lost the primary.

She was one of a handful of Republicans who supported a civil unions bill that was blocked in the state House.

Public Advocate of the United States did not respond to an email seeking comment.

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