The Mayor of Los Angeles is stepping all over what's long been called "the third rail of California politics," Proposition 13, which passed in 1978. Property taxes were on the rise, and people on fixed incomes were being taxed out of their homes. But Prop 13 didn't limit increases just for homeowners. It did so for business as well. Yesterday at the Sacramento Press Club, Antonio Villaraigosa called for change, a "split" tax roll, with different rules for homeowners than for business.