As a political professional, Karger--who for decades worked for one of California's premier campaign consulting firms, a shop that had helped invent modern opposition research--was grudgingly impressed with what the Mormons were doing. "They completely altered the landscape," he says. "They took over every aspect of the campaign." Karger estimates that Mormons ultimately contributed $30 million of the $42 million total raised in support of Prop 8, which passed easily in November 2008. (By contrast, anti-Prop 8 forces raised $64 million.)

But if the opponents of gay marriage won the battle, they also ensured themselves a big headache. In Karger, they galvanized an adversary who has now dug in to fight for the long haul--and who brings a dramatically different skill set than the rest of the marriage-equality movement. As Karger notes, most of the prominent gay-marriage advocates are, well, married people: risk averse and unschooled in the political dark arts. "I'm a different kind of gay activist," he says. "I'm a little wilder."