Democratic gubernatorial candidate Karl Dean has received the endorsement of the Human Rights Campaign, the nation's largest LGBTQ rights organization.

HRC's endorsement of a candidate in a Tennessee governor's race, announced Sunday at a fundraiser for Dean, is a rare — and possibly unprecedented — decision for the group.

The organization and Dean's campaign weren't immediately sure whether HRC has previously endorsed a gubernatorial candidate in Tennessee.

"Karl is the clear choice for Tennessee’s fair-minded voters who want a brighter, stronger future moving Tennessee forward as a welcoming and inclusive state," JoDee Winterhof, HRC senior vice president, said in a statement. "HRC is proud to endorse Karl Dean for governor, and we look forward to working with him to advance LGBTQ equality in The Volunteer State.”

While mayor of Nashville from 2007 to 2015, Dean signed into law an employment non-discrimination ordinance to protect LGBTQ people and was the first in Tennessee to join a national coalition of mayors in support of marriage equality.

HRC says it has identified 259,000 “equality voters" in Tennessee, or those who claim to be strong supporters of progressive LGBTQ policies such as marriage equality, equitable family law, and laws banning discrimination based on sexual orientation or gender identity.

Dean's opponent, Republican nominee Bill Lee, has said he believes marriage is between a man and a woman and wants to see more children adopted in “traditional” families.

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In a statement, Dean said he was "grateful" to HRC for its endorsement, noting that he and the organization "both believe Tennessee’s future success depends on being a welcoming, inclusive state where everyone is treated with dignity and respect."

"The more we celebrate our diversity and the more open we are, the stronger we’ll be," Dean said.

Reach Natalie Allison at nallison@tennessean.com. Follow her on Twitter at @natalie_allison.

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