50%??? The burgeoning vote that will put Schwarzenegger over the top consists of disaffected young educated techies in Silicon Valley, suburban Riordan/Wilson Republicans, Independents who know the Dems are selling them out to illegals, Unions and environutzoids but are turned off by the Abortion-obsessed chanters and gun loving militiamen they associate with the GOP ... but mostly his surge will come from young apolitical College folk, Warehouse, cashier and waitstaff and cosmotologist and customer service grunts and gruntettes, military folk and legally resident immigrants or native born work a day folk from Mexico and China who Arnold touches as an immigrant who made it. They're not making the poll numbers, they'll come from nowhere because Arnold has rendered this election a statement making event. These same people WILL NOT vote for McClintock in a Senate race against Boxer. They like Arnold, he's honest and he's going to serve their interest even if they're not sure what their interest is.
Unyielding social conservatives are going to sit in their 10% phone booth and compliment themselves and each other for achieving nothing in a principled manner.
Ask your self, "Why are moderates moderate?" I would say it is because they have tended to reject the more extreme or devisive social policies of either the liberals or the conservatives. When it comes to fiscal policies, I sense that the majority of the moderates tend to lean conservative. (It was the political humourist, P. J. O'Roarke, who said that "a liberal was defined as a person who would give his neighbor's checking account to the poor."). I think it is the fiscally conservative moderates who are motivated to vote.
My sense is that the true liberals will stay home. Suppose on 1/3 of them vote (not unrealistic, because only about 1/2 of eligible voters overall will actually vote). About 2/5 of the moderates will turnout. About 3/4 of the conservatives will vote (they smell blood). Based on the 30-50-20 registration of political ideology, and recalculated, you get roughly 47-40-13.
Not withstanding your description of the types of voters you believe are motivated to vote in this recall election, most of the voters in this election will be those who tend to vote in election after election. I honestly don't see a great groundswell of "new" voters coming to the polls. I see this election turning on the relative abundance of the core voters in each of the demographic groupings.