Proposition 13 (approved by voters in 1978) is the reason California is ungovernable. It caps California's ability to collect property tax revenue and makes raising other forms of revenue almost impossible (by requiring a supermajority of 66.7% for any new taxes). At the same time, it did not cap the state's ability to increase spending, or increase obligations through new ballot propositions. The result is that California is stuck in the death grip of the 2 Santa Claus Theory of Politics -- the idea that we can cut taxes and increase spending at the same time. The 2 Santa Claus Theory has been a winning political strategy for almost 30 years now -- it's also bankrupted the State of California and turned us into a 2nd or 3rd world state.
But here's the thing: Proposition 13 is unconstitutional (yeah I know it was upheld as constitutional by the U.S. Supreme Court in Nordlinger v. Hahn -- but the constitutional theory I'm about to lay down was not tested in that case). Proposition 13 is unconstitutional because a simple majority cannot impose a supermajority requirement upon the rest of the population.
Proposition 13 passed with 64.8% of the vote -- well short of the 66.7% supermajority it imposed on the state constitution for raising new revenues. A supermajority requirement gives 34% of the population veto power over the rest of the state's population -- which is a violation of the one person one vote principle guaranteed by the 14th and 19th Amendments to the U.S. Constitution. A supermajority requirement gives a certain type of voter -- one who opposes tax increases -- the power of 2 votes for every 1 vote cast by a tax supporter. (If my side is required to get 66.7% of the vote to pass something and the other side only has to get 34% of the vote to kill something -- each of their votes is worth roughly twice my vote).
To illustrate the point, let's amplify the dynamics underlying Proposition 13: Let's say I really really hate the drilling of new oil wells in the State of California. So I put together a ballot initiative that says, "any new oil well in the state of California can only be passed if 99% of the residents in the district approve of it." And then I succeed in passing the ballot measure with 51% of the vote. Thus a simple majority would have succeeded in forcing a supermajority requirement upon the actions of future voters in that district -- just as Proposition 13 did to the State of California. But in the process the voters would have violated the one person one vote doctrine. Each anti-oil well vote is now equal in weight to 99 votes from those who support a new oil well. Although I might really really like to pass such a law, because I hate new oil wells, it's unconstitutional to arbitrarily give some votes more weight than others.
Just as the 99% supermajority in the example above is arbitrary, so too the 66.7% supermajority contained in Proposition 13 is also arbitrary. My example increases the power of a certain class of voters by 99 times, Proposition 13 increases the power of a certain class of voters by 2 times -- but any violation of the ONE person ONE vote principle should be unconstitutional. (It is also interesting to note that, in fact, older white Republican voters are the class who benefited most from the democracy-distorting effect of Proposition 13).
The 2/3rds requirement of Proposition 13 seems to be based on the number of votes necessary in the U.S. Senate to override a Presidential veto. But that proves the point. Proposition 13 gives the power of the veto, normally reserved for the Executive Branch, to one class of voters (anti-tax voters) -- while relegating all other voters (pro-tax voters) to second class status.