Nate Silver has an interesting take at 538:
Certainly, the No on 8 folks might have done a better job of outreach to California’s black and Latino communities. But the notion that Prop 8 passed because of the Obama turnout surge is silly. Exit polls suggest that first-time voters — the vast majority of whom were driven to turn out by Obama (he won 83 percent [!] of their votes) — voted against Prop 8 by a 62-38 margin. More experienced voters voted for the measure 56-44, however, providing for its passage.
Now, it’s true that if new voters had voted against Prop 8 at the same rates that they voted for Obama, the measure probably would have failed. But that does not mean that the new voters were harmful on balance — they were helpful on balance. If California’s electorate had been the same as it was in 2004, Prop 8 would have passed by a wider margin.
Furthermore, it would be premature to say that new Latino and black voters were responsible for Prop 8’s passage. Latinos aged 18-29 (not strictly the same as ‘new’ voters, but the closest available proxy) voted against Prop 8 by a 59-41 margin. These figures are not available for young black voters, but it would surprise me if their votes weren’t fairly close to the 50-50 mark.
At the end of the day, Prop 8’s passage was more a generational matter than a racial one. If nobody over the age of 65 had voted, Prop 8 would have failed by a point or two. It appears that the generational splits may be larger within minority communities than among whites, although the data on this is sketchy.
The good news for supporters of marriage equity is that — and there’s no polite way to put this — the older voters aren’t going to be around for all that much longer, and they’ll gradually be cycled out and replaced by younger voters who grew up in a more tolerant era. Everyone knew going in that Prop 8 was going to be a photo finish — California might be just progressive enough and 2008 might be just soon enough for the voters to affirm marriage equity. Or, it might fall just short, which is what happened. But two or four or six or eight years from now, it will get across the finish line.