Josh Mandel, the Republican working to unseat Ohio Senator Sherrod Brown, has vowed to fight gay marriage.

At a tea party rally in support of Ohio Treasurer Mandel at the Sharonville Convention Center, Mandel addressed a crowd of 300 for about 30 minutes, the Cincinnati Inquirer reported.

Mandel said he is fighting Brown on the issue of gay nuptials and will “protect the sanctity of marriage.”

“This is a fight that I will never, ever back down,” he said.

Joining Mandel at the rally was Republican Senator Mike Lee of Utah.

Sadie Weiner, campaign manager for Friends of Sherrod Brown, criticized Mandel's remarks.

“Josh Mandel's vow to continue fighting against equal rights is a slap in the face to Ohio families,” Weiner told gay weekly The Washington Blade. “LGBT Ohioans face discrimination and intimidation for their sexual orientation every day. Unfortunately, Josh Mandel's position only adds fuel to the fire.”

As a member of the Ohio House, Mandel voted against a gay workplace protections measure.

Brown, a strong advocate for gay rights, in 2010 delivered an impassioned speech against gay teen bullying on the Senate floor.