I sent Rick Claussen's memo, referenced below, to Mark Baldassare of PPIC, and asked him for a response to the claims on voter turnout. Here's what Mark wrote back:

"Thanks, our poll does not assume a specific turnout for the
election. In fact, we never make predictions about the size and
composition of the electorate before an election. We define likely
voters through answers to a series of questions about voter
registration, intentions to vote, past voting, interest in politics, and
attention to election news. Rather than focus on the size of our sample
as it relates to the percent of registered voters, let's consider the
partisan makeup among our likely voters -- Democrat 45%; Republicans
36%; dts/others=19%. Would a low turnout produce a more Republican or a
more Democratic electorate? This will be important, since Republicans
are  opposed to 1A to 1E will Democrats favor each of them...."

UPDATED 9 p.m.: Rick Claussen, the veteran initiative consultant handling the sweeping campaign for all six California special election measures, is out with an interesting memo on the recent PPIC poll, which shows five of those six in trouble.

Claussen is self-interested obviously. But your blogger has found him to be very reliable in the past. (Most recently, your blogger said Prop 11, last November's redistricting initiative in California, had no chance of passing. Claussen told me I was wrong and then proved it, managing the campaign that got it passed).

In this new memo, dated Wednesday, Claussen writes that the PPIC poll effectively assumes a turnout of 50 percent. He says the campaign's own internals on Prop 1A show it with a lead of 50 to 37 percent. That would make the measure hardly a sure thing, but that's much better than the PPIC poll, which showed it trailing, with 46 percent No and 39 percent Yes:

From the memo:

The headlines from this morning's new Public Policy Institute of California poll all focus on Prop 8. But there isn't much surprising in those numbers. Evangelicals and Republicans overwhelmingly supported Prop 8. No kidding. The poll also documented the intensity gap between Prop 8's supporters (74 percent considered the outcome of Prop 8 very important) and its opponents (59 percent considered the outcome very important).

This is a crucial study from the Public Policy Insitute of California on the state's water challenges. It calls for a building a peripheral canal to carry water around the Sacramento-San Joaquin Delta. The reasons are complicated, but the politics could be dangerous. The 1982 ballot measure to establish a peripheral canal was defeated, a major political event (that helped to spawn the state's ballot measure industry).