The Campaign for California Families (CCF) is the rival to the Yes on 8 folks, but they're even more extreme in their beliefs, not only believing that same-sex marriage should be illegal but also any sort of recognition of gay relationships whatsoever.
CCF attempted to intervene on Strauss vs. Horton, which the Yes on 8 folks opposed, and they were denied. Then on August 19 they tried to intervene on Perry vs. Schwarzenneger (aka Prop 8 case), but Judge Walker denied their motion. They appealed to the 9th Circuit Court and appeared in a hearing earlier this month.
The Recorder reported that the panel's judges appeared unsympathetic to CCF's Attorney Staver's attempt to identify CCF's particular interest as a proposed Perry party. Staver argued "that the official Prop 8 forces weren't adequately litigating the case and had stipulated away far too many facts" about gays and lesbians.