The requirement for a 2/3 vote comes from Proposition 13, which was hardly
backed by "landed gentry."

The thinking by Jarvis/Gann and its proponents at the time was that
while general sales taxes are opposed by lots of people (hence they
require only 50% + 1 for passage), special sales taxes usually were
projects backed by local, powerful, politically connected special interests
and frequently supported by local media. (Remember this was 1977 when
Prop 13 was drafted.)

So, according to the history on this proposition, the designers specifically inserted the 2/3
requirement to "level the playing field" for taxpayer groups with
limited resources to oppose the proposed special sales tax measures, backed
by special interests.

It seems to have worked that way in Marin and Sonoma. When they tried
to circumvent the 2/3 requirement with an "A/B" split [A for advisory, and
B for a general sales tax] in 1998, voters rejected handing over a
"blank check" to the politicians. It didn't even get
to 50% required to pass a general sales tax. Both counties voting on separate
measures had similar results.

The requirement for passing some school funding measures has been lowered
a bit. There has been ongoing discussion to lower the requirement for
transportation infrastructure projects. The problem that proponents of
lowering the hurdle rate have is that many of the transportation measures do garner
a 2/3 vote. Only the dogs (like the SMART proposal) can't seem to
get to 2/3.

Maybe that tells you something about the SMART proposal.