The top tax rate in CA is 9.3% but the bracket is some ridiculously low figure like everything above $50,000/yr (for singles) is taxed at the top rate so effectively for most educated people their marginal rate would be 9.3% and any increase would affect most middle class people.
Increasing the tax rate to 12% is an EXTREMELY bad idea, count me among those who will seriously consider leaving CA if this happens. I pay ludicrously high taxes as it is.