From the moment it became clear last fall that Democrats won supermajorities of slightly more than two-thirds in both houses of the California Legislature, Proposition 13 has been in the political crosshairs. That’s a sea change for the landmark 1978 initiative that limits property taxes to 1 percent of the 1975 assessed value or 1 percent of the latest sales price, allowing yearly increases of no more than 2 percent to adjust for inflation. No one has seriously proposed going back to the pre-13 system of taxing properties based on their current market value, which often saw levies double or …