Dennis Hollingsworth is the defendant in the Prop 8 case. His political career began in 2000 when Hollingsworth was elected to the California State Assembly, then the California State Senate in 2002. In 2010, he retired from the Senate because of term limitations. He also served as California State Minority Leader from 2008 - 2010.
How did he become the Prop 8 defendant? Hollingsworth leads ProtectMarriage.com, an anti-gay website. The site was formed in 2002 though, far before he became affiliated with this case. The goal of the site is to "defend and restore the definition of marriage as between a man and a woman."
Fun fact: Hollingsworth majored in Dairy Sciences in college.